Chapter 3: Overview of future changes in climate

Chapter description

This chapter synthesizes the detailed assessments in chapters 4 to 9 on future changes in climate across Canada, including changes in the atmosphere, in freshwater, on land, in ice and snow, and in the oceans around Canada, and provides a synthesis and a detailed assessment of future changes in average temperature, precipitation, and near-surface wind.

Chapter key messages

Plain language summary^{Footnote 1}

Canada’s climate is changing rapidly and will continue to change in the near term, regardless of how emissions change. In the longer term, many aspects of Canada’s climate will stabilize if global carbon dioxide emissions are reduced to net zero, but the changes will intensify if emissions stay high. This chapter first synthesizes projections of future changes in climate across Canada, drawing on the detailed assessments later in this chapter and in chapters 4 to 9. This synthesis complements Chapter 2, which provides similar information for past changes in climate across Canada. Second, this chapter assesses projected changes in average temperature, precipitation, and near-surface wind across Canada. These are core climate variables that exert a key influence on other aspects of the climate system, as well as on human societies and ecosystems.

Compared to the first edition of Canada’s Changing Climate Report (CCCR2019)(Bush & Lemmen, 2019), we place greater emphasis on the near term (2021–2040), which is important for many stakeholders, and over which climate change is relatively insensitive to the emissions scenario considered. We assess that Canada is projected to warm by approximately 0.9°C between 2021 and 2040, continuing the past warming trend for Canada. Many past trends are projected to continue, including trends towards more frequent hot extremes, less frequent cold extremes, earlier peak streamflow, warmer and more acidic waters around Canada’s coasts, and increasing area burned by wildfire.

For the longer term (through to 2100), we provide a discussion and an assessment of global scenarios and the assumptions that underly them. While the five scenarios based on the shared socio-economic pathways (SSPs) assessed in this chapter represent only a subset of possible global futures and are based on a limited set of underlying assumptions and worldviews, recent literature does support an assessment that high emissions scenarios are now less probable than they were thought to be when CCCR2019 was published. At the same time, new approaches to constraining projections with observations allow us to narrow the range of projected warming under any given scenario compared to that assessed in CCCR2019. These approaches, when applied to the most recent model simulations, result in a higher level of projected average warming than the projections based on equivalent scenarios assessed in CCCR2019.

A scenario roughly representative of current global climate policies (SSP2-4.5) has global emissions of greenhouse gases declining towards the end of the century, but corresponds to a future climate for Canada that is far from benign. Under this scenario, Canada is projected to warm through the century, reaching a median estimated warming 5°C by 2081–2100 relative to 1850–1900, while warming is more likely than not^{Footnote 2 Footnote 3} to exceed 10°C in much of Nunavut in winter. Also under this scenario, glaciers in Western Canada are projected to lose more than 75% of their ice, intense precipitation is projected to increase by a median estimate of 40% in Canada as a whole, and the central Arctic Ocean is likely to be ice-free most Septembers. Moreover, Canada is projected to still be warming at the end of the century under this scenario. In a scenario with no global climate policies and increasing emissions (SSP3-7.0), future climate change in Canada is projected to be substantially more severe even than that projected under the current-policies scenario. By contrast, in a low emissions scenario (SSP1-2.6), in which the world reaches net-zero carbon dioxide emissions around 2075, Canada’s climate is projected to stabilize in the second half of this century. Under this scenario, the amount of additional human-induced warming in the future is projected to be less than the human-induced warming to date. Nonetheless, even in this net-zero scenario, Canadian average warming is projected to reach a median estimate of 3.5°C above pre-industrial (approximated in this report as 1850–1900) levels in 2081–2100, with some changes, such as glacier melt and sea level rise, being only slightly reduced compared to the current-policies scenario. These findings emphasize the need to adapt to and plan for climate change even in such a net-zero future.

Overall, the synthesis we provide in this chapter shows Canada’s future climate becoming increasingly clear: climate change is no longer an abstract problem for the future, but one that we are very much already experiencing, with future changes that we can now anticipate with greater confidence.

3.1: Introduction

Climate projections are simulations of future climate created using mathematical models of the Earth’s climate system. They are called projections rather than predictions because they rely on assumptions about the driving factors of climate change, such as human emissions of greenhouse gases. Projections are key to understanding how Canada’s climate will change in the future, to planning adaptation measures to reduce impacts, and to understanding how our future climate depends on the choices Canada and other countries make regarding greenhouse gas emissions. This chapter provides a synthesis of future changes in climate across Canada, drawing on the detailed assessments later in this chapter and in chapters 4 to 9 (Figure 3.1). This chapter therefore complements Chapter 2, which provides a similar synthesis for past changes in the Canadian climate system. Together, the syntheses in chapters 2 and 3 provide a stand-alone overview of the findings in the entire report. In the second part of this chapter, we provide a detailed assessment of changes to Canada’s core near-surface climate variables: temperature, precipitation, and near-surface wind.

The synthesis in this chapter (section 3.2) focuses first on projections for the near term (2021–2040), an important time frame to many decision-makers, and for which projected ongoing climate change is largely insensitive to emissions scenario. For time periods beyond 2040, we focus first on long-term climate change under a scenario approximately consistent with current global climate policies (SSP2-4.5). We then discuss long-term climate change under a scenario that reaches net-zero global carbon dioxide (CO₂) emissions in the second half of this century (SSP1-2.6). Finally, we discuss long-term climate change under a scenario with no climate policies and progressively increasing emissions (SSP3-7.0), which would represent a global rollback or failure of existing climate policies.

Since this is the first chapter in the report to use climate projections, we next describe how climate projections are made, and the sources of uncertainty in those projections (section 3.3). This section of the chapter includes a discussion of the scenarios underlying our assessment, including the assumptions underlying those scenarios. This is followed by a discussion of the uncertainty associated with the climate response, and how that uncertainty can be constrained using observations of the climate and climate change. Finally, we include a discussion of the influence of natural variations within the climate system, or internal variability, on future Canadian climate, as well as the use of decadal predictions to predict those variations in the near term.

Next, this chapter covers our primary, detailed assessment of future changes in seasonal and annual average temperature and precipitation across Canada (sections 3.4 to 3.5). These climate variables exert key influences on ecosystems, agriculture, hydroelectricity, heating and cooling loads on buildings, and many other systems. Temperature and precipitation also drive changes in other components of the climate system assessed in this report, including changes in freshwater, the cryosphere, Canada’s oceans, and the land carbon cycle, including phenomena such as wildfires. This chapter assesses changes in average temperature and precipitation, including snowfall, whereas changes in temperature and precipitation extremes are assessed in Chapter 8. This chapter’s assessment includes changes in average temperature and precipitation for Canada, as well as changes averaged over regions of Canada, and shows maps of spatial patterns of projected changes. Finally, we also briefly assess future changes in near-surface wind speed across Canada (section 3.6), a variable that is important for wind energy availability, among other things.

3.2: Synthesis of projected changes

Key message 3.1: Canada’s near-term future climate

In the near term, Canada will continue warming at close to twice the global rate, with an increase of about 0.9°C (0.2–1.6°C) from 2021 to 2040 in all emissions scenarios (high confidence). On average over this 20-year period, Canada is projected to be 2.7°C (1.8–3.6°C) warmer (high confidence) and receive 7% (5–10%) more precipitation (medium confidence) compared to the 1850–1900 average. Trends already observed, towards more frequent hot extremes, earlier peak streamflow, warmer and more acidic waters around the coasts, and increasing area burned by wildfire, are projected to continue (high confidence). The duration of snow, sea ice, and lake ice cover in Canada will shorten with every increment of global warming (very high confidence).

Key message 3.2: Canada’s long-term future climate under current global climate policies

Climate change in Canada will intensify through the century if emissions continue on a path approximately consistent with current global climate policies (high confidence). In 2081–2100, average warming across Canada relative to 1850–1900 is projected to reach 5.0°C (3.8–6.6°C) (high confidence), and precipitation is projected to increase by 13% (9–18%) (medium confidence). The intensity and frequency of heavy precipitation are projected to increase (high confidence). There is medium confidence that atmospheric rivers will strengthen. Glaciers in western Canada are projected to lose more than 75% of their mass (medium confidence), and permafrost thaw in northern Canada will continue (very high confidence).

Key message 3.3: Canada’s long-term future climate in a net-zero world

Most aspects of Canada’s climate will stabilize in the second half of this century if global CO₂ emissions immediately start to decline and reach net zero in the 2070s (high confidence). Under such a scenario, Canadian temperatures are projected to warm by about 0.8°C between the 2021–2040 and 2081–2100 periods, reaching 3.5°C (2.3–4.8°C) above 1850–1900 average temperatures (high confidence). However, because of slow response times, sea level in most coastal areas is projected to continue to rise, glaciers to continue to melt, and permafrost to continue to thaw through the century, even after surface temperatures stabilize (high confidence).

Key message 3.4: Canada’s long-term future climate in a world with no climate policies

Climate change will continue to intensify strongly in all regions of Canada if emissions continue to rise throughout the century (high confidence), which would reflect a scenario in which current global climate policies are rolled back or fail to mitigate global emissions. In 2081–2100 under this scenario, Canadian temperatures are projected to increase to 6.9°C (5.2–8.9°C) above the 1850–1900 average (high confidence). Precipitation is projected to increase on average by 17% (12–24%) for Canada as a whole (medium confidence), with larger increases in the intensity and frequency of heavy precipitation events than under the current-policies scenario (high confidence). Atmospheric rivers over Canada are projected to strengthen (high confidence), while summer drought is projected to intensify in southern Canada (high confidence). With higher warming levels, the duration of snow, sea ice, and seasonally frozen ground in Canada is projected to shorten even more than under current global climate policies, and glacier melt, permafrost thaw, and sea level rise along most of Canada’s coasts are projected to be higher (high confidence).

This section synthesizes information on future climate change in Canada over two main timescales. First, we synthesize information on climate change in Canada over the near term (2021–2040) (section 3.2.1). This period has already begun but was chosen for consistency with the near-term period used in the Working Group I (WGI) contribution to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) (IPCC AR6 WGI) (2021). The near term is of particular interest for many climate change adaptation and planning activities, where decisions are being made on timescales of up to 10 to 20 years and can be evaluated and adjusted as climate evolves. Such adaptation can often substantially reduce climate risks. On this timescale, climate change is not strongly dependent on emissions scenario, minimizing one source of uncertainty. Furthermore, over the first five years, climate models initialized with the observed states of the atmosphere and ocean can often produce predictions that outperform uninitialized climate model projections for some climate variables (section 3.4.1), and such predictions are also summarized here.

The second timescale focused on here is the second half of the 21st century, with a particular emphasis on the late century (2081–2100) (sections 3.2.2 to 3.2.4). Climate change over this period, which is important for many adaptation decisions relating to long-lived infrastructure, resource planning, ecosystems, and society, is sensitive to emissions scenario. In most climate change adaptation and planning activities, it is important to consider a range of scenarios, rather than just one, in order to account for differences in risks under different emissions scenarios (Chapter 10, section 10.5.1). In particular, for sectors that are very sensitive to high levels of warming and have little opportunity to adjust responses, risk-based decision-making may have to take into account high emissions scenarios, which are less consistent with current emissions trends (section 3.3.1) but can have a high impact. By contrast, when planning horizons are shorter, or when adaptive measures can be adjusted as more information becomes available, adaptation and planning decisions may not have to take high emissions scenarios into account.

The projections in this report are based on climate model simulations of the response to a limited number of emissions scenarios that cover a range of future emissions from very low to very high (see section 3.3.1 for a discussion of the scenarios and Figure 3.4 for associated CO₂ emissions). In this synthesis section, we focus first on a scenario roughly consistent with currently implemented global climate policies, in which global greenhouse gas emissions remain relatively constant until about 2050 and then decline gradually thereafter (SSP2-4.5) (section 3.2.2). We then contrast this with a scenario in which global CO₂ emissions are rapidly reduced, reaching net zero around 2075 (SSP1-2.6), where net zero represents a state where any remaining human-caused CO₂ emissions are balanced by an equal amount of human-caused CO₂ removal from the atmosphere (section 3.2.3). This scenario would be approximately consistent with all countries delivering on their pledged emissions reductions and net-zero goals, which would require the successful implementation of additional national climate policies beyond those currently in effect. We focus on this scenario rather than the more stringent SSP1-1.9, the only scenario in which end-of-century global warming is more likely than not to be below 1.5°C (IPCC, 2021), because SSP1-1.9 simulations are available only from a limited number of climate models. Finally, we show results for a high emissions scenario (SSP3-7.0) (section 3.2.4), which is a scenario with no climate mitigation policies, in which global greenhouse gas emissions progressively increase (section 3.3.1). We focus on this scenario rather than the very high emissions scenario (SSP5-8.5) because several recent analyses have suggested that current global climate policies have decreased the likelihood that future emissions will increase at the pace represented in the very high emissions scenario (section 3.3.1).

In this section, we generally use a pre-industrial baseline (approximated in this report as 1850 to 1900) to compare projections, for reasons outlined in Chapter 2, section 2.1. Briefly, this baseline period is consistent with the baseline period generally used for projections in the IPCC AR6 WGI report (IPCC, 2021). While the Industrial Revolution did begin before 1850, the effect of anthropogenic (human-caused) emissions on global temperatures before this period is estimated to be small (Chen et al., 2021), and a lack of observations prior to 1850 limits the use of earlier baseline periods. The 1850–1900 period is also consistent with the reference period typically used for the 1.5°C and 2°C global warming levels referenced in the Paris Agreement and in this report, and it allows the net effects of cumulative emissions in different scenarios to be compared. For some climate variables, projections relative to an 1850–1900 baseline period are not available in the underlying chapters and assessed literature. In those cases we report projections relative to other baseline periods. Note that the first edition of Canada’s Changing Climate Report (CCCR2019) used a baseline period of 1986–2005 for temperature and precipitation projections, which was about 0.7°C warmer in the global average than the 1850–1900 baseline period used here (Gulev et al., 2021). Information on Canadian warming over a range of baseline periods is available in Chapter 2, Box 2.4.

In the synthesis sections that follow, the chapter and section numbers that support each conclusion are provided in brackets. For example, “5.4” refers to Chapter 5, section 5.4. Bracketed ranges for changes in variables assessed in this chapter indicate 5–95% uncertainty intervals, meaning that except where noted otherwise, there is assessed to be a 90% chance that the true value will fall within this range.

3.2.1: Canada’s near-term future climate

This section synthesizes projections for Canada over the near term (2021–2040) (see also Figure 3.2). Over this period, we report projections under an intermediate emissions scenario, SSP2-4.5, but these projections are not very sensitive to the scenario used. This is first because emissions in different global emissions scenarios beginning in 2015 have had little time to diverge from each other. Second, the cumulative global emissions of CO₂ since the 1850–1900 baseline period, which are the primary driver of global warming, diverge even less between scenarios over this period.

3.2.1.1: Temperature

Canadian average temperature is projected to rise by about 0.9°C (0.2–1.6°C) from 2021 to 2040, no matter how global emissions change (3.4). The level of projected warming is higher in the north than the south, and higher in the east than the west. Predictions from institutions around the world, including Environment and Climate Change Canada, indicate that there is more than an 80% chance that 2025–2029 will be warmer on average than 1991–2020 in both the warm and cold seasons everywhere in Canada. Canada is projected to be 2.7°C (1.8–3.6°C) warmer on average from 2021 to 2040 compared to 1850 to 1900, which is close to twice the projected global warming of 1.5°C (1.2–1.8°C) for the same period. Note that the Paris Agreement commits countries to pursuing efforts to limit global warming to this level.

Rising average temperatures will be accompanied by hotter and more frequent hot extremes and warmer and less frequent cold extremes in all regions of Canada (very high confidence) (8.2.2). The highest daily maximum temperature of the year, averaged over the country, is projected to rise by 2.6°C (2.0–3.1°C) for 2021 to 2040 relative to 1850 to 1900, which is similar to the projected rise in summer average temperatures. Projected changes are larger for cold extremes than for hot extremes. The lowest daily minimum temperature of the year is projected to rise faster than winter temperatures over Canada, averaging 4.7°C (3.7–5.6°C) warmer in 2021–2040 than in 1850–1900. Changes in the intensity of hot and cold extremes in Canada generally scale well with changes in the global average temperature (8.2.2).

3.2.1.2: Precipitation

From 2021 to 2040, Canadian average annual precipitation is projected to be 7% (5–10%) higher relative to the 1850–1900 baseline, with larger increases in winter and in the Canadian Arctic (3.5). Increases are projected in the intensity (the amount of rain in a given period) and in the frequency of heavy daily, multi-day, and sub-daily precipitation (high confidence) (8.3.1.2, 8.3.2.2). Changes in the intensity of precipitation extremes scale well with average temperature because higher temperatures increase the amount of water vapour the atmosphere can hold. This leads to an approximately 7% increase in the amount of precipitation for every 1°C increase in Canadian temperature for short-duration (sub-daily) rainfall (medium confidence) (Box 8.3). The projected rise in Canadian average temperature for 2021–2040 relative to 1850–1900 results in a projected increase in the intensity of heavy short-duration rainfall by 20% (13–28%). This means that, on average, the largest sub-daily rainfall event each year will have 20% more rain. There may be some differences from this scaling rate, depending on the region or duration of precipitation (8.3.1.2, 8.3.2.2, Box 8.3). Heavy precipitation events are also projected to become more frequent (high confidence) (8.3.1.2, 8.3.2.2).

3.2.1.3: Freshwater

Climate warming is causing an increase in the proportion of rainfall versus snowfall and more rainfall during the cold season, a trend that is projected to continue in the near term (5.2). Projections indicate that as a result of this larger amount of rainfall, annual streamflow levels will rise in northern Canada in the near term. Seasonal streamflow levels will rise across most of Canada during winter and early spring and will fall during summer and autumn (high confidence). Finally, spring streamflow across Canada will continue to peak earlier because of the earlier onset of the spring freshet (higher flows resulting from spring thaw), which in turn is due to the higher temperatures in the spring.

In the near term, surface water levels are projected to drop in lakes and wetlands in some regions and rise in others (5.4). The direction of change is dependent on the balance between increased open-water evaporation due to higher temperatures and longer ice-free periods, and projected increases in precipitation. Surface water in northern regions will continue to be affected by permafrost thaw, which will cause lakes and wetlands to expand in some regions and disappear in others. Groundwater is expected to remain one of the sources of freshwater that is more resilient to the effects of a changing climate (high confidence) (5.5).

There are several factors driving changes in flooding that can act in opposing ways. Rising temperatures and more rainfall can increase the frequency of rapid snowmelt and rain-on-snow–induced floods. Meanwhile, less snowfall and thinner ice cover may reduce numbers of spring floods, including those related to river ice jams. It is therefore uncertain how snow- and ice-related floods will change in the near term. (5.7)

3.2.1.4: Cryosphere

The duration of snow cover is projected to shorten across all of Canada with each increment of global warming (6.2.3). Most parts of the country are projected to lose 1 to 2 weeks of seasonal snow cover per degree Celsius of global warming. While the Arctic Ocean is expected to have some ice cover in summer in most years, it is about as likely as not that in September, the month with the minimum ice cover, the central Arctic Ocean will be ice-free at least once by 2040 (6.3.3.2). The annual ice-free period in regions where sea ice forms and melts each year is projected to lengthen (high confidence). Averaged over the Arctic, this period is projected to be about 31 days longer per degree Celsius of global warming (6.3.3.1), which for the near term implies an additional 47 days compared to the 1850–1900 baseline. These changes are projected to happen faster in the Beaufort Sea and more slowly in the Labrador Sea (medium confidence). The Northwest Passage is not expected to be consistently ice-free in the near term (6.3.3.3). The duration of lake ice cover is projected to be 10 to 21 days shorter per degree Celsius of global warming (6.4.3.2), resulting in a decrease of 15 to 32 days compared to 1850–1900 for the near term. The annual number of days with seasonally frozen ground and the maximum annual depth of seasonally frozen ground are both expected to decrease across Canada (6.6.3).

3.2.1.5: Ocean

The oceans around Canada are expected to continue to experience rising sea surface temperature during ice-free periods (7.2). In the recent past, this rise has been largest off the coast of southern Atlantic Canada, but during the summer, warming has been observed everywhere off the coast of eastern Canada, including Hudson Bay. Projections indicate that this warming trend will continue with the largest annual average warming expected off the coasts of Atlantic Canada and British Columbia, and with the most warming in the summer expected in Hudson Bay and the Beaufort Sea (7.2.2). The rise in ocean temperature has led to more frequent and hotter marine heatwaves, a trend expected to continue with future increases in ocean temperature. Past decreases in sea surface salinity will continue because of more precipitation and runoff from land, including glacier and ice sheet meltwater (7.3.2). The warming and freshening of the sea surface due to climate change is expected to result in the upper ocean becoming more stratified in the northeast Pacific and off the coast of southern Atlantic Canada, affecting the vertical transport of physical, chemical, and biological materials that are crucial for marine ecosystems.

Across Canada, the sea level will continue to change relative to the land in the near term, and the amount and direction of change will vary regionally, since vertical land motion varies a great deal across the country (7.4.2). Projected changes in relative sea level through the current century are largely scenario-independent before about 2050. Since land is gradually sinking in parts of Atlantic Canada and the western Arctic because of post-glacial adjustment, these regions are projected to experience a higher rise in sea level than the global average. Where relative sea level is projected to rise, extreme sea level events, which are driven by storm surges, waves, and tides, will become larger and more frequent, posing risks to coastal communities (7.6). These risks include increased coastal flooding, infrastructure and ecosystem damage, and erosion of sandy coastlines.

3.2.1.6: Carbon cycle and ecosystems

Atmospheric CO₂ concentration is increasing mainly because of global anthropogenic CO₂ emissions from the burning of fossil fuels (9.3). How much CO₂ builds up in the atmosphere is affected by the cycling of carbon through the land, ocean, and atmosphere. Globally, land and ocean carbon sinks absorb about half of annual anthropogenic CO₂ emissions. This absorption has slowed the rate of growth of CO₂ in the atmosphere. Historically, Canada’s land area has taken up carbon, driven largely by increased plant and tree growth in response to increasing CO₂ concentrations, known as the CO₂ fertilization effect. However, since reliable Canada-wide records have been available (beginning in the early 1980s), the forest area burned by fires in Canada has increased. Projections indicate that this trend will continue. Therefore, although Canada’s carbon sink on land is expected to continue in the near term, the trend in forest area burned (9.5.1.7), along with changes in other factors such droughts, nutrient levels, and pests, makes the future of this carbon sink highly uncertain.

On average, the ocean inside Canada’s Exclusive Economic Zone is a net carbon sink. However, in most nearshore areas, it is a net source. The ocean will continue to be a net sink for CO₂ in the near term as long as atmospheric CO₂ continues to increase (9.5.2). The chemistry of the oceans around Canada will continue to be affected by climate change in the near term (7.7). Continued increases in CO₂ in the atmosphere will lead to more acidification of the ocean surface waters. The higher temperature and stratification of the upper ocean will reduce oxygen concentrations in deeper waters.

Changes in physical climate will inevitably alter land, freshwater, and marine ecosystems in the near term. Changes in temperature, precipitation, and the cryosphere, including extreme events, will affect Canada’s terrestrial and freshwater ecosystems (9.5.1). Increased acidification, decreased oxygen levels, ocean warming, and sea ice decline will impact marine ecosystems (6.3, 7.2, 7.7, Box 7.1).

3.2.2: Canada’s long-term future climate under current global climate policies

This section synthesizes projections for Canada under a scenario that is roughly consistent with current global climate policies, SSP2-4.5, also referred to in other chapters of this report as an intermediate emissions scenario (see also Figure 3.2).

3.2.2.1: Temperature

Under this scenario, Canadian average temperature is projected to rise progressively through this century, with an average warming that reaches 5.0°C (3.8–6.6°C) in 2081–2100 relative to the 1850–1900 baseline (3.4). Global warming is projected to surpass the Paris Agreement long-term temperature goal, reaching 2.0°C (1.6–2.5°C) in 2041–2060, and 2.7°C (2.1–3.5°C) in 2081–2100 (Table 3.1). In Canada, both winter and annual average warming are projected to be higher in the north than in the south and higher in the east than the west (3.4.2). In the summer, projected warming is relatively uniform across the country. Average warming in winter is projected to exceed 10°C by the end of the century over large parts of Nunavut and Nunavik (northern Quebec). Canada is also projected to continue warming beyond the end of the century (3.4).

More intense and frequent hot extremes and less intense and frequent cold extremes are projected across Canada, proportional to the ongoing average warming (very high confidence) (8.2.2). Cold extremes will warm more than hot extremes. The highest daily maximum temperature of the year (hottest day of the year), averaged over the country, is projected to be 4.6°C (3.6–6.0°C) hotter in 2081–2100 than in 1850–1900, which is similar to the change projected for Canadian summer average temperatures. The lowest daily minimum temperature of the year (coldest night of the year), averaged over the country, is projected to be 8.4°C (6.5–10.9°C) warmer in 2081–2100 than in 1850–1900, continuing to warm faster than Canadian winter average temperatures. Increases in the highest daily maximum and lowest daily minimum temperatures of the year are also projected for all regions of Canada. Cold extremes are projected to become rarer, while hot extremes are projected to become more common, and the more extreme the event, the faster its frequency is projected to change. Cold extreme events that occurred on average once every few decades in the recent past are projected to become virtually nonexistent under the level of warming projected for the late century under current global policies.

Fire weather extremes due to compound hot, dry, and windy conditions are projected to become more frequent and severe in most regions (high confidence) (8.7.1). Human-perceived heat stress based on combined hot temperatures and high humidity levels is also projected to increase with rising temperatures (high confidence) (8.7.4). There has been interest in the question of whether north-south meandering of the jet stream will increase this century, as it has been hypothesized that such an increase would influence future temperature extremes in Canada. However, there is no clear evidence that north-south meandering of the jet stream will increase. Year-to-year temperature variations associated with the El Niño–Southern Oscillation, currently limited mainly to western Canada, are projected to extend to central and eastern Canada (low confidence) (4.8).

3.2.2.2: Precipitation

Under this scenario, Canadian average annual precipitation is projected to increase by 13% (9–18%) by 2081–2100 relative to 1850–1900. The largest relative increases in seasonal average precipitation, at over 50%, are projected in winter and fall in Nunavut. Summer precipitation is likely to increase in the north (medium confidence) but may decrease in southernmost Canada (low confidence) (3.5).

Precipitation extremes are projected to increase in intensity and frequency (high confidence), largely driven by the increases in atmospheric moisture that come with warming temperatures (8.3.1.2, 8.3.2.2, Box 8.3). In addition, there is medium confidence that atmospheric rivers, which are linked to persistent heavy precipitation and damaging winds, will become stronger and more frequent (4.5). Environmental conditions that favour convective storms are also projected to occur more often, particularly across central and eastern Canada in spring, summer, and fall (medium confidence) (4.7). Jet streams and associated storm tracks, extratropical cyclones, and atmospheric rivers are projected to migrate poleward (low confidence) (4.3–4.5). The magnitude of short-duration (sub-daily) heavy rainfall, averaged over Canada, is projected to increase by approximately 40% (29–56%) compared to 1850–1900, in accordance with the increase in Canadian average temperature in 2081–2100 (8.3.2.2). The magnitude of annual maximum one-day and five-day precipitation is also projected to increase (8.3.1.2). Similar changes are projected for most regions, with larger increases in northern Canada. Smaller changes are projected in the Prairies. The frequency of heavy precipitation Canada-wide is also projected to increase, with larger changes in frequency for rarer events (8.3.1.2, 8.3.2.2). Compound wind and rainfall events will also become more frequent (medium confidence) (8.7.3). Freezing rain forms only in a narrow range of air temperatures both aloft and at the surface, and this influences the regional patterns of projected increases and decreases in freezing rain. Freezing rain is expected to become more frequent in the Prairies and less frequent in southern Ontario and Atlantic Canada. Little change in freezing rain is projected over the rest of Canada (3.5).

3.2.2.3: Freshwater

Streamflow is projected to increase in the winter across Canada and annually in northern Canada under this scenario (high confidence) (5.3). Summer flows in western Canada are projected to decrease (high confidence). Spring streamflow will peak earlier in the year than at present, resulting in shifts from more snowmelt-dominated to more rainfall-dominated streams. Lake and wetland water levels are projected to drop in some regions and rise in others because of the many complex factors that affect surface water storage (medium confidence) (5.4). Groundwater will be recharged earlier in the year because of earlier snowmelt and more winter rainfall (high confidence) (5.5). Groundwater is expected to remain a source of freshwater that is more resilient to the effects of a changing climate than surface water (medium confidence). Projected increases in extreme precipitation are expected to make rainfall-related urban floods more common (high confidence) (5.7). The earlier occurrence of snowmelt, ice jam breakups, and rain-on-snow events due to warmer temperatures is projected to shift the timing of streamflow-related spring floods to earlier (high confidence). However, the future frequency of such floods remains uncertain due to the interactions between rising temperatures, decreased snow cover, and the complex dynamics of snowmelt-related floods. Future meteorological and agricultural droughts are projected to be longer and more frequent and intense across central and southern Canada during summer (high confidence) (5.6).

3.2.2.4: Cryosphere

Annual snowfall is projected to increase in northern Canada, but it is projected to decrease in southernmost Canada, particularly in coastal regions (medium confidence) (3.5.2). Climate models project most parts of Canada will lose 1–2 weeks of seasonal snow cover per degree Celsius of global warming (in this scenario global warming is projected to reach 2.7°C by the late century) (6.2.3). The intensity and frequency of extreme one-day snowfall events are projected to increase over most of northern Canada (medium confidence), because of increases in atmospheric moisture and precipitation, and warming cold season temperatures that remain below 0°C (8.3.3.2). There is low confidence in the future magnitude and direction of change of extreme snowfall events for southern Canada (8.3.3.2). The central Arctic Ocean is likely to be ice-free in most Septembers (6.3.3.2). Averaged over the Arctic, the annual ice-free period in regions where sea ice forms and melts each year is projected to get about 31 days longer per degree Celsius of global warming. This means that compared to 1850–1900 the annual ice-free period will be about 84 days longer in 2081–2100 under this scenario. These changes are projected to be smaller in the Labrador Sea and larger in the Beaufort Sea (medium confidence). The duration of lake ice cover in Canada is projected to be about 10 to 21 days shorter per degree Celsius of global warming, implying that the ice cover season will be 27 to 57 days shorter in 2081–2100 than it was in 1850–1900 (6.4.3.2). Glaciers in western Canada are projected to lose 75–100% of their 2015 mass by 2100, with a median estimate of 94%, while glaciers in the northern Canadian Arctic are projected to lose 10–26% (6.5.3). Permafrost warming and thaw-driven landscape changes are expected to increase further with additional climate warming (very high confidence) (6.7.3). However, there is low confidence regarding the magnitude and timing of these changes and the extent to which they will be affected by local ground characteristics.

3.2.2.5: Ocean

Under this scenario, sea surface temperatures are projected to rise by 1.2 to 3.2°C in the oceans around Canada by the late century relative to 1990–2014 (7.2.2). The regional pattern of projected sea surface temperature change is similar to what has been observed historically, with waters off the coasts of southern Atlantic Canada and British Columbia projected to warm the most. However, changes in summer temperature are projected to be large in Hudson Bay and the southern Beaufort Sea because loss of summer sea ice will be an important factor in these areas.

The sea level is projected to fall relative to the land in Hudson Bay and much of the eastern Arctic, where land uplift rates are high (7.4). Where the land is rising less quickly, relative sea level is projected to rise, and where the land is sinking, relative sea level is projected to rise the most, exceeding the projected global increase of 0.56 m (0.44–0.76 m) by 2100 relative to 1995–2014 in much of Atlantic Canada and the western Arctic. Tuktoyaktuk and Halifax are in parts of Canada where the land is sinking, and they have the highest projected rise in sea level of the locations assessed. In Rimouski, Vancouver, and Tofino, the land is rising slowly. Therefore, these locations will experience a lower rise in the sea level. In contrast to those five communities, the relative sea level is projected to fall in Churchill, on the coast of Hudson Bay, in this scenario because the land there is rising quickly. A 0.5-m rise in relative sea level above 1995–2014 levels is unlikely to be reached before about 2055 in most coastal communities in Canada under this scenario (7.4.2.2).

The Atlantic Meridional Overturning Circulation is a system of ocean currents that moves sinking, cold sub-Arctic waters south, and warmer surface waters north, bringing vast amounts of heat into the North Atlantic. A weakening of this system will slightly reduce the warming of eastern and northern Canada. Its collapse would make eastern and northern Canada much cooler and cannot be ruled out in this scenario. However, we have medium confidence that any such shutdown will not occur during the 21st century (4.9).

3.2.2.6: Carbon cycle and ecosystems

Increased atmospheric CO₂ causes global warming that will be effectively irreversible for centuries to millennia. Atmospheric CO₂ concentrations are projected to continue to increase throughout the century under this scenario, despite moderate decreases in CO₂ emissions in the second half of the century. As long as CO₂ emissions continue (remain above net zero), as they do throughout the century under this scenario, Canada and the globe will continue to warm (9.4.1). The area burned by wildfire each year is increasing, and this trend is projected to continue (9.5.1.7). Although plants and trees are expected to become more productive in Canada because of a higher amount of CO₂ in the atmosphere, emissions from fire, permafrost thaw, and other disturbances are also expected to increase. These counteracting processes make the net effect on the carbon balance of Canada's land ecosystems uncertain. Overall, the ocean inside Canada’s Exclusive Economic Zone will continue to absorb CO₂, similar to the global ocean, in response to continuing increases in atmospheric CO₂, and as a result, the ocean will continue to acidify (7.7.2, 9.5.2).

3.2.3: Canada’s long-term future climate in a net-zero world

In the low emissions scenario, SSP1-2.6, global CO₂ emissions begin to decline after 2020 and reach net zero around 2075. Global CO₂-equivalent emissions of all greenhouse gases decline significantly in this scenario, but do not reach net zero before the end of the century. This section synthesizes projections for Canada under this net-zero scenario (see also Figure 3.2).

3.2.3.1: Temperature

Global warming is closely proportional to cumulative CO₂ emissions. This means that global warming will continue until global CO₂ emissions reach net zero. After that point, declining CO₂ concentrations and other climate forcings are projected to lead to mostly stable global average temperature (9.4). In this scenario, the rise in global average temperature is likely to remain below 2°C (Table 3.1). Canadian average temperature is projected to stabilize in the latter half of the century, warming about 0.8°C between the periods 2021–2040 and 2081–2100 (Table 3.1) (3.4). In this scenario, the climate is projected to warm less in the future than it already has to date (2.4).

Canadian average temperature is projected to be 3.5°C (2.3–4.8°C) warmer in 2081–2100 than the 1850–1900 baseline period, about twice the global warming of 1.8°C (1.3–2.4°C) over the same period (3.4). Hot and cold temperature extremes are projected to stabilize in Canada in the second half of this century, as changes in these extremes scale linearly with changes in the global average temperature. The highest daily maximum temperature of the year (hottest day of the year), averaged over the country, is projected to be 3.1°C (2.2–4.1°C) warmer than in 1850–1900, and the lowest daily minimum temperature of the year (coldest night of the year) 5.6°C (4.0–7.4°C) warmer (8.2.2).

3.2.3.2: Precipitation

In this scenario, average precipitation and precipitation extremes are also projected to stabilize in Canada in the second half of this century. Canadian average precipitation is projected to increase by a median estimate of only 2.5% between the periods 2021–2040 and 2081–2100 (3.5). The intensity of heavy short-duration rainfall is projected to be 27% (17–38%) higher in 2081–2100 than in 1850–1900 (8.3.2.2).

3.2.3.3: Freshwater

Few studies have investigated freshwater changes in Canada under this scenario. However, given that temperature and precipitation are projected to stabilize under this net-zero scenario, streamflow and other freshwater changes are also expected to stabilize in Canada (5.3). Future meteorological and agricultural droughts are projected to increase in frequency in southern Canada, although less so than in the current-policies or no-policies scenario (medium confidence) (5.6).

3.2.3.4: Cryosphere

Snow cover and sea ice area are also projected to stabilize in the second half of the century under this scenario (6.2, 6.3). The duration of annual lake ice cover is projected to be 10 to 21 days shorter per degree Celsius of global warming, meaning 18 to 38 fewer days per year on average in 2081–2100 than in 1850–1900 under this net-zero scenario (6.4). Whether the central Arctic Ocean will be consistently ice-free in September is uncertain, but it will likely be occasionally ice-free (6.3.3.2). However, because of their slow response times, glacier melt and permafrost thaw are projected to continue through the century even after global net-zero CO₂ emissions have been reached (6.5, 6.7). By the end of the century, glaciers in western Canada are projected to lose about 55–97% of their 2015 mass, while glaciers in the northern Canadian Arctic are projected to lose about 8–24%, only slightly less than under the current-policies scenario.

3.2.3.5: Ocean

Under this net-zero scenario, sea surface temperatures in all regions of the oceans around Canada are projected to rise 0.7 to 2.1°C by the late century relative to 1990–2014 (7.2.2). These values are lower than the values for the projected rise in sea surface temperatures under the current-policies scenario, but the regional patterns—which parts of the oceans warm more or less quickly—are similar.

Global mean sea level will continue to rise for thousands of years, even if future CO₂ emissions are reduced to net zero and global warming halted, as excess heat due to past emissions continues to slowly spread into the deep ocean, and as glaciers and ice sheets continue to melt, contributing meltwater to the oceans. The projected changes in sea level for Canada are largely the same to about 2050 regardless of scenario (7.4). By the end of the 21st century, this net-zero scenario is projected to result in a global average rise in sea level that is about 12 cm less than under the current-policies scenario. An alternative way to consider sea level projections is by noting the future year in which a given rise in sea level is reached. A 0.5-m rise in relative sea level above 1995–2014 levels is unlikely to be reached before about 2060 in most coastal communities in Canada under a low emissions scenario (7.4.2.2).

3.2.3.6: Carbon cycle and ecosystems

In this net-zero scenario, atmospheric CO₂ concentrations are projected to peak and then decline in the last decades of this century. Achieving net-zero emissions in this scenario would require anthropogenic CO₂ removal from the atmosphere to offset hard-to-mitigate residual emissions. In Canada, deliberate actions to enhance CO₂ uptake and storage on land and in the ocean could draw down some additional CO₂ from the atmosphere. While these actions could provide several important co-benefits, their potential to sequester CO₂, and thereby contribute to achieving net zero, is modest. Furthermore, the timescale of carbon storage in vegetated ecosystems (seasons to a century) is short relative to the timescale of committed warming from previous carbon emissions from the burning of fossil fuels (millennia). Nonetheless, protecting existing vegetated ecosystems on land and in the ocean would maintain their ability to act as sinks, and may prevent some additional emissions of greenhouse gases (9.6.2).

In this low emissions scenario, the area burned by wildfire each year is projected to increase in the near term (2021–2040), but then to stabilize at around 50% above the area burned in the period from 1998 to 2014 (9.5.1.7). The acidity of the ocean surface around Canada is projected to increase by 20–35% by the end of the century relative to current values, and the largest changes are projected in the Arctic and northwest Atlantic (7.7.2).

3.2.4: Canada’s long-term future climate in a world with no climate policies

Under a high emissions scenario with no climate policies and no mitigation of greenhouse gas emissions (SSP3-7.0), global greenhouse gas emissions are projected to progressively increase throughout the century. Projections for Canada under this scenario are synthesized in this section (see also Figure 3.2).

3.2.4.1: Temperature

Under this scenario, Canadian average temperature is projected to rise strongly, reaching 6.9°C (5.2–8.9°C) above the 1850–1900 baseline levels in 2081–2100 (3.4). The corresponding rise in global average temperature is 3.6°C (2.8–4.6°C), about half the warming projected for Canada (3.4). In this scenario, with a high warming level, hot extremes in Canada are projected to become much more frequent, and cold extremes much less frequent, and both hot extremes and cold extremes are projected to be much warmer (8.2.2). Averaged across Canada, by 2081–2100 the highest daily maximum temperature of the year (hottest day of the year) is projected to rise by 6.2°C (4.8–7.9°C) relative to 1850–1900, while the lowest daily minimum temperature of the year (coldest night of the year) is projected to rise by 11.2°C (8.7–14.3°C). Hot extremes are projected to occur more often, with larger changes for rarer events. For cold extremes, the temperatures that occurred on average once every few decades in 1850–1900 become virtually impossible under this level of additional warming. Extreme fire weather in most regions, due to compound hot, dry, and windy conditions, and human-perceived heat stress, based on combined hot temperatures and high humidity levels, are both projected to become more frequent and severe (high confidence) (8.7.1, 8.7.4). Year-to-year temperature variations linked to the El Niño–Southern Oscillation, currently limited mainly to western Canada, are projected to extend to central and eastern Canada (low confidence) (4.8).

3.2.4.2: Precipitation

Under this no-policies scenario, and averaged across Canada, the amount of annual average precipitation is projected to be 17% (12–24%) higher in 2081–2100 than in 1850–1900 (medium confidence) (3.5). Projected increases in precipitation exceed 50% over a large part of northern Canada in winter (medium confidence). Projected decreases in precipitation in southernmost Canada in summer are larger than under the current-policies scenario, although there is low confidence in these projected decreases. For this same period, and averaged across Canada, the amount of rainfall in short-duration (sub-daily) heavy precipitation events is projected to reach 59% (42–83%) above 1850–1900 levels because of the increased water-holding capacity of a warmer atmosphere (8.3.2.2, Box 8.3). The amount of precipitation in one-day and multi-day heavy precipitation events is also projected to increase (8.3.1.2, Box 8.3). Atmospheric rivers are projected to become stronger and more frequent (high confidence) (4.5). Environmental conditions that favour convective storms are also projected to become more common, particularly across central and eastern Canada (high confidence) (4.7).

With increasing global warming, freezing rain is projected to become more frequent over most of Canada due to an increase in the occurrence of atmospheric temperature conditions that favour its formation. This is particularly so for the Canadian Prairies and some mountainous regions of British Columbia and the Northwest Territories, which are projected to have up to 25 more hours of freezing rain per year. By contrast, freezing rain is projected to decrease over southern Ontario and Atlantic Canada (3.5)

3.2.4.3: Freshwater

Under this scenario, freshwater changes in Canada are projected to intensify more than under the other scenarios. Meteorological and agricultural droughts (dry conditions leading to soil moisture deficits) are projected to be longer and more frequent and intense across central and southern Canada, particularly in summer (high confidence). The duration, frequency, and intensity of summer hydrological droughts (low water availability) are also projected to increase in many parts of southern Canada, mainly due to increased evaporation and lower runoff from mountainous regions (low confidence) (5.6).

3.2.4.4: Cryosphere

The central Arctic Ocean is likely to be ice-free every September (6.3.3.2). Averaged over the Arctic, the annual ice-free period in regions where sea ice forms and thaws each year is projected to be about 31 days longer per degree Celsius of global warming (high confidence), which under this scenario implies that the ice-free period will be 112 days longer in 2081–2100 than in 1850–1900. The annual period of lake ice cover is projected to be about 10 to 21 days shorter per degree Celsius of global warming, implying 36 to 76 days less ice cover in 2081–2100 than in 1850–1900 (6.4.4.1). Glaciers in western Canada are projected to virtually disappear by the end of the century in this scenario (6.5.3). Global climate models project 45 fewer frost days on average by the end of the century relative to a recent baseline period under this scenario, which implies a corresponding shorter duration of seasonally frozen ground (6.6.3). Permafrost warming and thaw-driven landscape changes are expected to increase with additional climate warming in this scenario (high confidence) (6.7.3).

3.2.4.5: Ocean

Under this no-policies scenario, sea surface temperatures in all regions of the oceans around Canada are projected to get much warmer, rising by 2.5 to 4.2°C by the late 21st century relative to 1990–2014 (7.2.2). These values are higher than the values for projected sea surface warming under the current-policies scenario. Summertime warming in Hudson Bay and the southern Beaufort Sea is projected to exceed 5°C. The regional pattern of projected annual temperature change is similar to that under other scenarios.

By the end of the 21st century, under this no-policies scenario, global mean sea level is projected be about 12 cm higher than under the current-policies scenario (3.2.2.5). A 0.5-m rise in relative sea level above 1995–2014 levels is likely by 2080 for southern Atlantic Canada (for example, Halifax) and the southern Beaufort Sea (for example, Tuktoyaktut). In other regions of Canada, a 0.5-m rise in relative sea level is projected to occur after 2100. Even under this scenario, with high emissions and high warming levels, relative sea level will continue to fall in the Hudson Bay area because of the rapid land uplift in the region (7.4.2.2).

An expected weakening of the Atlantic Meridional Overturning Circulation will slightly reduce the warming of eastern and northern Canada. While a complete shutdown of this ocean current system cannot be ruled out, we have medium confidence that any such shutdown will not occur during the 21st century (4.9).

3.2.4.6: Carbon cycle and ecosystems

Under this scenario, continued rising global CO₂ emissions are projected to lead to a faster build-up of CO₂ in the atmosphere throughout this century. Annual area burned in Canada is projected to increase substantially, reaching more than three times the average area burned in 1998–2014 by the end of the 21st century (9.5.1.7). Ocean acidity is projected to double by the end of the century in most of the surface waters around Canada, with even larger changes expected in the Arctic and northwest Atlantic (7.7.2).

3.2.5: Confidence terms in key messages: summary of evidence

Key message 3.1: Canada’s near-term future climate

In the near term, Canada will continue warming at close to twice the global rate, with an increase of about 0.9°C (0.2–1.6°C) from 2021 to 2040 in all emissions scenarios (high confidence). On average over this 20-year period, Canada is projected to be 2.7°C (1.8–3.6°C) warmer (high confidence) and receive 7% (5–10%) more precipitation (medium confidence) compared to the 1850–1900 average. Trends already observed, towards more frequent hot extremes, earlier peak streamflow, warmer and more acidic waters around the coasts, and increasing area burned by wildfire, are projected to continue (high confidence). The duration of snow, sea ice, and lake ice cover in Canada will shorten with every increment of global warming (very high confidence).

Key message 3.2: Canada’s long-term future climate under current global climate policies

Climate change in Canada will intensify through the century if emissions continue on a path approximately consistent with current global climate policies (high confidence). In 2081–2100, average warming across Canada relative to 1850–1900 is projected to reach 5.0°C (3.8–6.6°C) (high confidence), and precipitation is projected to increase by 13% (9–18%) (medium confidence). The intensity and frequency of heavy precipitation are projected to increase (high confidence). There is medium confidence that atmospheric rivers will strengthen. Glaciers in western Canada are projected to lose more than 75% of their mass (medium confidence), and permafrost thaw in northern Canada will continue (very high confidence).

Key message 3.3: Canada’s long-term future climate in a net-zero world

Most aspects of Canada’s climate will stabilize in the second half of this century if global CO₂ emissions immediately start to decline and reach net zero in the 2070s (high confidence). Under such a scenario, Canadian temperatures are projected to warm by about 0.8°C between the 2021–2040 and 2081–2100 periods, reaching 3.5°C (2.3–4.8°C) above 1850–1900 average temperatures (high confidence). However, because of slow response times, sea level in most coastal areas is projected to continue to rise, glaciers to continue to melt, and permafrost to continue to thaw through the century, even after surface temperatures stabilize (high confidence).

Key message 3.4: Canada’s long-term future climate in a world with no climate policies

Climate change will continue to intensify strongly in all regions of Canada if emissions continue to rise throughout the century (high confidence), which would reflect a scenario in which current global climate policies are rolled back or fail to mitigate global emissions. In 2081–2100 under this scenario, Canadian temperatures are projected to increase to 6.9°C (5.2–8.9°C) above the 1850–1900 average (high confidence). Precipitation is projected to increase on average by 17% (12–24%) for Canada as a whole (medium confidence), with larger increases in the intensity and frequency of heavy precipitation events than under the current-policies scenario (high confidence). Atmospheric rivers over Canada are projected to strengthen (high confidence), while summer drought is projected to intensify in southern Canada (high confidence). With higher warming levels, the duration of snow, sea ice, and seasonally frozen ground in Canada is projected to shorten even more than under current global climate policies, and glacier melt, permafrost thaw, and sea level rise along most of Canada’s coasts are projected to be higher (high confidence).

The above synthesis is based on the detailed assessments in sections 3.4 and 3.5 and in chapters 4 to 9. The following is a discussion of the strength of the evidence underlying each statement in the key messages, including justification for synthesis assessments made in this section.

With respect to Key Message 3.1, an assessment of the rate of Canadian warming compared to global warming can be found in section 3.4.2, which finds on the basis of multiple lines of evidence that Canada is projected to warm at close to twice the global rate. This finding is consistent with assessments made for both past and future warming in CCCR2019. We have high confidence in our assessed quantitative projections of temperature for Canada, as described in section 3.4.3. We therefore have high confidence in our assessment that Canada will continue warming by the amount indicated at close to twice the global rate in all emissions scenarios. We have medium confidence in our corresponding precipitation projection, as described in section 3.5.1. Bracketed ranges in this chapter indicate 5–95% uncertainty intervals, meaning that except where noted otherwise, there is a 90% chance that the true value will fall within this range. In Chapter 8, section 8.2 assesses with very high confidence that increases in the frequency of hot extremes are projected for all regions of Canada, with changes becoming larger as global average temperature increases, and it assesses with high confidence that increases in the frequency of hot extremes in Canada have been observed. In Chapter 5, section 5.3 assesses with high confidence that an observed change towards earlier peak streamflow is projected to continue. In Chapter 7, section 7.2 assesses with high confidence that ocean temperatures around Canada have increased and that projections under all future scenarios show continued warming in the oceans around Canada. In Chapter 7, section 7.7 assesses with very high confidence that ocean acidification has occurred at the surface of the oceans around Canada and that over the rest of the 21st century, Canada’s oceans are projected to continue to increase in acidity. In Chapter 9, section 9.5 assesses with high confidence that an observed trend towards an increasing area burned by wildfire in Canada is expected to continue. Together these assessments support a confidence level of at least high for all the assessments in the third sentence of this key message. Chapter 6 assesses as a statement of fact that with each increment of global warming, snow cover duration is projected to shorten across Canada (section 6.2) and the ice-free period across Canadian ocean waters is projected to lengthen (section 6.3). It also assesses with very high confidence that lake ice duration is projected to shorten across Canada with each increment of global warming (Chapter 6, section 6.4). We therefore have very high confidence in our assessment that with each increment of global warming, the duration of snow, sea ice, and lake ice cover in Canada will be shorter.

With respect to Key Message 3.2, our high confidence that climate change in Canada will intensify through the century under the SSP2-4.5 scenario, which is roughly consistent with current climate policies, is supported by the progressive warming through the century projected under this scenario for the globe (IPCC, 2021) and Canada (section 3.4), as well as the progressive increases projected in precipitation (section 3.5), sea level (Chapter 7, section 7.4), and many other variables. We have high confidence in our assessed quantitative projections of temperature for Canada and medium confidence in corresponding precipitation projections, as described in sections 3.4.3 and 3.5.1, respectively. In Chapter 8, section 8.3 assesses with high confidence that the intensity and frequency of short-duration (shorter than one-day) rainfall extremes and one-day and five-day heavy precipitation extremes in Canada are projected to increase in the future. We therefore have high confidence that the intensity and frequency of heavy precipitation are projected to increase. Our medium confidence that atmospheric rivers will strengthen under this scenario is based on the assessment in Chapter 4, section 4.5. In Chapter 6, section 6.5 reports that one study projected a decrease in glacier mass in western Canada of 94 ± 19% (75–100%) by 2100 relative to 2015 under RCP4.5 (similar to SSP2-4.5), which we summarize here as a projected loss of more than 75%. We have medium confidence in this assessment because, while this is based on a single study and considers a slightly different period and region than that considered here, this projection is consistent with projections based on earlier literature assessed in CCCR2019. In Chapter 6, section 6.7 assesses with very high confidence that permafrost warming and thaw-driven landscape changes are expected to increase further with additional climate warming, with some thawing continuing at depth even if climate stabilizes. We therefore have very high confidence in our assessment that permafrost thaw will continue in this scenario.

With respect to Key Message 3.3, our high confidence that most aspects of Canada’s climate are projected to stabilize in the second half of this century under the SSP1-2.6 scenario, in which global CO₂ emissions reach net zero in the 2070s, is based on the stabilization of global average temperature (IPCC, 2021) and Canadian average temperature (section 3.4) in the second half of this century projected under this scenario. It is also based on the finding that most aspects of Canadian climate change scale closely with global average temperature. We have high confidence in our assessed quantitative projections of temperature for Canada, as described in section 3.4.3. The IPCC AR6 WGI (IPCC, 2021) assessed that it is virtually certain that the global mean sea level will continue to rise in the current century, based on assessments across all the scenarios that we consider in this report. Consistent with this, Chapter 7 projects in section 7.4 that sea level will continue to rise through the century under SSP1-2.6 in locations around Canada’s coasts that are not experiencing substantial land uplift. In Chapter 6, section 6.5 assesses with very high confidence that Canada’s glaciers will continue to lose mass under every emissions scenario assessed. In Chapter 6, section 6.7 assesses with very high confidence that some permafrost thaw will continue at depth even if climate stabilizes, as it does under this net-zero scenario. We therefore have at least high confidence that sea level in most coastal areas is projected to continue to rise, glaciers to continue to melt, and permafrost to continue to thaw through the century.

With respect to Key Message 3.4, our assessment that rising emissions through the century in a scenario in which current policies are rolled back or fail to mitigate emissions (SSP3-7.0) will cause climate change to intensify strongly in all regions of Canada is primarily based on projections of warming for Canada and its subregions under SSP3-7.0 assessed in section 3.4. Since all regions of Canada show very high warming levels under this scenario (section 3.4), we have high confidence in this assessment. We also have high confidence in our assessed quantitative projections of temperature for Canada, as described in section 3.4.3. We have medium confidence in our projections of average precipitation changes, as assessed in section 3.5. In Chapter 8, section 8.3 assesses with high confidence that increases in the intensity and frequency of short-duration rainfall extremes, and one-day and five-day precipitation extremes will become larger as global average temperature increases. Projected global warming is higher under this no-policies scenario than under the current-policies scenario, as assessed by the IPCC AR6 WGI (IPCC, 2021). We therefore have high confidence that larger increases in the intensity and frequency of heavy precipitation events are projected under the no-policies scenario than the current-policies scenario. Our high confidence that atmospheric rivers are projected to strengthen under the no-policies scenario is based on the high confidence in Chapter 4, section 4.5, that the intensity of atmospheric rivers over Canada will increase in high emissions scenarios. Our high confidence that summer drought is projected to intensify in southern Canada is based on the high confidence in Chapter 5, section 5.6, that future meteorological and hydrological droughts are projected to be more intense in southern Canada during summer, particularly at the end of the century and at higher amounts of global warming. Chapter 6 assesses as a statement of fact that with each increment of global warming, snow cover duration is projected to shorten across Canada (section 6.2) and the ice-free period across Canadian waters is projected to lengthen (section 6.3). In Chapter 6, section 6.7 assesses with high confidence that the annual number of days with seasonally frozen ground and the maximum annual depth of seasonally frozen ground are expected to further decrease across Canada to the end of the century and beyond in this no-policies scenario. It also shows that projected decreases in the closely associated number of frost days are larger for this scenario that for the current-policies scenario. We therefore have high confidence that with higher warming levels, the duration of snow, sea ice, and seasonally frozen ground in Canada is projected to shorten even more under the no-policies scenario than the current-policies scenario. In Chapter 6, section 6.5 provides projections of glacier melt that are higher under high emissions scenarios than intermediate emissions scenarios, while section 3.4 shows that glacier melt is driven by climate warming, which is higher under high emissions scenarios. In Chapter 6, section 6.7 assesses with very high confidence that permafrost warming and thaw-driven landscape changes are expected to increase further with additional climate warming. It also reports more Northern Hemisphere permafrost thaw under a high emissions scenario than a low emissions scenario. In Chapter 7, section 7.4 shows a higher projected rise in sea level under this no-policies scenario than the current-policies scenario along most of Canada’s coasts, with the exception of parts of Hudson Bay and the eastern Arctic where relative sea level is projected to fall because of land uplift. We therefore assess with high confidence that glacier melt, permafrost thaw, and sea level rise along most of Canada’s coasts are projected to be higher under this no-policies scenario than the current-policies scenario.

Figure take-away: Future climate-related changes in Canada would be much larger under current or weaker policies than in a net-zero future.

Figure title: Synthesis of future climate change in Canada

Figure 3.2: Synthesis of future changes in Canadian climate under different emissions scenarios. The black line shows estimated average temperature anomalies (differences from the 1850–1900 average) for Canada, based on historical simulations to 2014 and on SSP2-4.5 simulations after. The blue line shows projections for SSP2-4.5 (a scenario that is approximately equivalent to current policies); the green line shows projections for SSP1-2.6 (a net-zero scenario), and the red line shows projections for SSP3-7.0 (a no-policies scenario). Shading shows 5–95% uncertainty ranges. Boxes show changes in key indicators for the near term (2021–2040) and long-term (2081–2100). For projections of western Canada glacier mass, the changes are median estimate anomalies in 2100 relative to 2015 under the nominally equivalent RCP2.6, RCP4.5, and RCP8.5 from Rounce et al. (2023), as reported in Chapter 6, section 6.5; for projections of Canadian area burned, anomalies are relative to 1998–2014 (Chapter 9, section 9.5.1.7); and for projections of Tuktoyaktuk sea level rise (Figure 7.22), anomalies are relative to 1995–2014. The Canadian average warming trend (section 3.4.2) is a linear trend over 20 years, and the probability of an ice-free central Arctic Ocean in September (Chapter 6, section 6.3.3) is expressed as a percentage. Changes are expressed relative to 1850–1900 for the other five indicators. Extreme precipitation refers to the Canada-wide average percentage change in short-duration (sub-daily) precipitation. The numbers in the boxes are median estimates (see section 3.2 for uncertainty ranges). Changes in hottest day of the year refer to the Canadian average annual maximum temperatures and are based on results presented in Chapter 8, section 8.2.2. Near-term indicators are shown for the current-policies scenario only, although most indicators are not strongly sensitive to scenario choice for this period. Dashes indicate that the report does not include an assessment of the change in that indicator for that period and scenario combination.

Case Story 3.1: A story of the seasons in Ulukhaktuuq, Northwest Territories

Recommended citation:

Farnole, P., Pogotak, A., Memogana, K., Stoller, M., Monahan, A., & Steiner, N. (2026). A story of the seasons in Ulukhaktuuq, Northwest Territories [Case Story 3.1]. In Canada’s Changing Climate Report 2026. (pp. xx–xx). Government of Canada. DOI for the chapter.

Community review: Olokhaktomiut Hunters and Trappers Committee

Summer ends with the waves getting bigger, shaking the pebbles on the shore. Their sound tells the fish that it is time to gather at the river mouth to travel upstream. It is also time for students to go back to school. We can still do some net or rod fishing in the ocean, and berry picking. Fish, musk-oxen, caribous, and rabbits are fattier, and seals begin to rebuild the blubber they lost over springtime. Birds too have gained fat, and start migrating back south as the land turns white. It is a good time for hunting and trapping, but it is cooling off fast, and getting dark earlier.

Fall starts with the freezing of the shoreline on the ocean side, which tells us that the lakes are frozen as well, and we can soon begin lake fishing through the ice, jigging, or setting up nets. Caribou mate before migrating for the winter, males and females following separate trails. Days are really short, and the ocean freeze-up can be delayed by the winds or the warmer ocean. With thin ice, we stay near town and travel along the shoreline, often to set traps or hunt wolves that can come right into town. Delayed freeze-up and thin ice can also affect caribou migration routes.

Winter comes slowly as ice gets thicker and daylight longer again. It is a time for patience, staying indoors, especially for elders. It is a time for crafting, fixing things and telling stories. Further into winter, seals are really fat: it is a good time to practise our seal-hooking skills. When the Sun comes back, we get a couple of weeks of bad weather: the winds are raising the Sun (Qulvaqhaiyuq). Blizzards set the real cold. Snow gets tough like concrete, which is great for making igloos. It is the coldest time of the year: Qiqaunihaaq (February).

Spring comes with subtle signs. Winds smell and sound different. Did you see an icicle drip or a snowbird fly by? With daylight getting longer, people start venturing further away from town. Some cannot wait to go fishing, dig their way through thick ice, and jig for trout or char. Others are on the lookout for polar bears, brought by west winds. Snowdrifts are useful to find our way through a storm.

With long days and ice getting thinner, lake fishing is really booming. The Sun no longer sets, so don’t forget your sunglasses! Spring peaks with warmer days. Geese follow patches of bare earth to nest near watershed areas, ducks fly over cracks on the ocean, snow melts, and rivers can go anytime. May’s full moon brings bearded seal pups with the first bumble bee.

Summer finally comes, very quickly. When lake ice is gone, rivers heat up and push the sea ice away from shore. Get your nets ready for the char run. It’s boating season, and whales come in. Flowers are blooming, and berries getting juicier, especially after a couple of rainfalls. But mosquitoes also rise from the ground, welcoming us at summer camp.

When elders see the Earth shadow or the morning dew on Arctic cotton, they know summer is coming to an end. The weather will change soon: it is time to get ready for winter.

“When the Moon comes up laying down, there will be lots of animals. Back then we used to use the stars, the Sun and the Moon, but now we hardly use them. The Moon was their calendar, that’s why the words for Moon and Calendar are so close. Those were Inuk scientists. Astronomers.”
– Kate Kanayok Inuktalik

One of the motivations behind this work is to develop a dialogue between Inuit Qauyimayait and Western science around climate, through a mapping and study of the seasons from both standpoints (Case Story 3.1 Figure 1). The ice has changed over the past 50 years around Ulukhaktuuq. While each year is different, community members, climate models, and satellite observations all indicate a longer open-water duration. Breakup used to happen in mid-July but is now in June. Freeze-up used to be around mid-October but now can be delayed until December.

Climate models can help simulate future conditions (Case Story 3.1 Figure 2). Projections show more and more years with 6+ months of open water towards the end of the century. In this sci-fi modelling world, we experimented with students to imagine what the calendar could look like 50 years from now. Community members were interested in such projected calendars as pedagogic tools for younger generations to support local adaptation to future changes. However, knowledge holders insisted on keeping them separate from traditional knowledge for two reasons:

1. Projections could constitute a distraction from what makes young Inuinnait strong. Know your language and elders’ stories, keep your eyes and ears open, learn to listen to the land. Then, if you have time, look at future climate projections.
2. Accountability is a core value for Inuinnait Knowledge holders. Since projections touch intergenerational transmission, the further you look, the more accurate you need to be. You can’t afford to be wrong when planning for the next generations. Yet climate projections grow uncertain the further they run.

This calendar was designed as a map holding together language, stories, arts, and wisdom along with climate insights; as a frame of reference supporting a holistic understanding of the seasons; as an invitation to listen to the land and its seasonal call to action, at the core of Inuinnait resilience.

Figure title: Seasonal calendar for Ulukhaktuuq, Northwest Territories, and major contributors

Case Story 3.1 Figure 1: Calendar of the seasons (top) and major contributors to the calendar at community hall, Ulukhaktuuq (bottom). First row, left to right: Janine Harvey, Agnes Kuptana, Helena Ekootak, Robert Kuptana, Ross Klengenberg; second row, left to right: April Olifie, Mark Ekootak, Allen Pogotak, Pat Klengenberg, Koral Memogana, Mollie Oliktoak, Celine Joss, Adam Kuptana, Susie Memogana, Trent Kuptana.

Figure title: Past, present, and potential future seasonal calendars for Ulukhaktuuq, Northwest Territories

Case Story 3.1 Figure 2: Past and current calendars, based on Inuit Qauyimayait, and possible future calendar based on simulated and observed open-water duration.

3.3: Climate projections and their uncertainties

Key message 3.5: Uncertainties in climate projections result from uncertainties in future emissions of greenhouse gases and other climate change drivers, uncertainties in how the climate system will respond to those changes, and internal climate variability. The range of plausible future global emissions has shifted towards lower emissions scenarios, partly because of developments in global policy and technology (medium confidence). For each emissions scenario, climate response uncertainty has narrowed, owing to improved synthesis of climate models and observations (high confidence). Some internal variability in Canadian climate can now be predicted for periods of up to five years (medium confidence), reducing this source of uncertainty in estimates of near-term climate.

Climate projections are generally made using climate models that are based on physical principles and driven by scenarios of future changes in emissions or concentrations of greenhouse gases and other climate change drivers. These scenarios are typically derived from integrated assessment models (IAMs) (Box 3.2), which simulate possible pathways of future social, economic, and technological change and their effects on emissions. Climate projections have three sources of uncertainty: emissions scenario uncertainty, climate response uncertainty, and internal climate variability (Hawkins & Sutton, 2009) (Figure 3.3). We discuss each in turn, and how they can be constrained.
Figure take-away: Uncertainty associated with future Canadian warming is dominated by internal climate variability and climate response uncertainty in the near term, and by emissions scenario uncertainty in the long term.

Figure title: Projections of Canada’s average temperature and their sources of uncertainty

Figure 3.3: Projections of changes in Canada’s average temperature and their sources of uncertainty. a) Projections of Canada’s 20-year-average surface air temperature difference from the 1850–1900 average under five SSP-based scenarios. Projections are constrained using observations and are an average of results derived using the approaches of Y. Liang et al. (2023), Cannon (2024), and Li et al. (2025), except for SSP1-1.9, which is based on unconstrained projections, due to the small number of models with output available for this scenario. SSP1-1.9 simulations were scaled such that their 1995–2014 average warming matched that of the Y. Liang et al. (2023) constrained projections under SSP2-4.5. b) Projection uncertainty that arises from internal climate variability (blue), climate response uncertainty (pink), and scenario uncertainty (grey). The times shown on the x-axis are the central years of each 20-year period. c) Relative importance of each source of uncertainty shown in panel b), quantified using fractional uncertainty.

3.3.1: Scenarios

To make projections, global climate models use different scenarios of future concentrations of greenhouse gases, as well as other climate change drivers, such as aerosols. These concentration scenarios, in turn, are based on emissions scenarios derived from integrated assessment models of how future human behaviour will affect emissions, which depend on uncertain political, societal, and technological changes. Translating changes in emissions to changes in concentration introduces other uncertainties related to the carbon cycle and other biogeochemical processes. The effect of these socio-economic and biogeochemical factors on the trajectory of future concentrations is referred to as scenario uncertainty in climate projections.

For the past several decades, the climate research community has developed scenarios to describe potential future pathways for emissions based on a range of demographic, economic, energy use, social, technological, and political variables (Chen et al., 2021). The current generation of scenarios is based on a set of five socio-economic storylines known as the shared socio-economic pathways (SSPs), namely, SSP1 to SSP5 (Ebi et al., 2014; Kriegler et al., 2014; Moss et al., 2010; O’Neill et al., 2014). These SSP storylines reflect imagined future socio-economic and technological changes, which are derived from a range of underlying assumptions about how the world is likely to evolve over the coming century (Box 3.2).

All of the SSP storylines were conceived of as plausible futures that represent a range of baseline societal conditions. Baseline emissions pathways without mitigation policies were also generated for each SSP storyline. The effect of climate mitigation policies on future emissions trajectories for each storyline was then explored. To generate a pathway of future emissions under different assumptions about climate mitigation, each SSP storyline was combined with a limit on radiative forcing (RF). RF refers to a change in the balance of the energy entering the Earth’s atmosphere minus the energy leaving it due to a change in the drivers of climate change, and is expressed in watts per square metre, or W/m². Positive RF indicates that more energy is entering the Earth’s atmosphere than leaving it, leading to climate warming. Lower RF in a scenario therefore means that mitigation has been more ambitious to limit the amount of climate warming, while higher RF means that mitigation has been less ambitious (Riahi et al., 2017; van Vuuren et al., 2011). Integrated assessment models are then used to estimate future emissions pathways that would be consistent with both the SSP storyline and a selected level of RF in 2100 (Riahi et al., 2017). A given future emissions scenario is therefore generated from a particular RF limit, socio-economic storyline, and integrated assessment model. For example, SSP1-1.9 refers to a scenario using the SSP1 storyline that limits human-caused RF to below 1.9 W/m² by the end of the 21st century.

From the full set of available SSP/RF/IAM combinations, the research community identified a set of illustrative scenarios that were used as input to generate projections from computationally expensive global climate models (Chen et al., 2021; O’Neill et al., 2017). The illustrative scenarios that are most widely used and that are discussed often in this report are SSP1-1.9 (very low emissions), SSP1-2.6 (low emissions), SSP2-4.5 (intermediate emissions), SSP3-7.0 (high emissions), and SSP5-8.5 (very high emissions). In the two scenarios with the most stringent climate targets, SSP1-1.9 and SSP1-2.6, CO₂ emissions rapidly decrease and reach net zero by around 2055 and 2075, respectively, and then become net-negative (where carbon removals exceed the level of remaining emissions) by the end of the 21st century. In SSP2-4.5, CO₂ emissions begin to decrease but do not reach net zero before the end of the century. In the high and very high emissions scenarios that do not include climate policy, SSP3-7.0 and SSP5-8.5, CO₂ emissions continue to increase throughout the 21st century (Figure 3.4).

Figure take-away: Global carbon dioxide emissions over the past 10 years were above those in low emissions scenarios and below those in high emissions scenarios.

Figure title: Observed and projected CO₂ emissions in illustrative emissions scenarios

Figure 3.4: Global carbon dioxide (CO₂) emissions (in gigatons of CO₂ per year) from fossil fuel combustion and land-use change. CO₂ as observed is shown by the black line ending in a red dot, indicating year 2024 emissions, and CO₂ as projected in the SSP-based scenarios is shown by the coloured lines. Thick lines represent the standard marker scenarios used as inputs to climate model simulations, and thin lines show variants of each scenario generated by other integrated assessment models. Note that this figure includes two additional marker scenarios (SSP4-6.0 and SSP4-3.4) that are not widely used in the modelling literature and are not assessed elsewhere in this report. Projected global warming in 2081-2100 relative to 1850-1900 (IPCC, 2021) is indicated next to the other scenario names. Source: Global Carbon Project (Friedlingstein et al., 2025).

CCCR2019 assessed projected changes in climate for Canada based on the previous generation of scenarios, which were not paired with SSP storylines. These scenarios were called representative concentration pathways (RCPs), and each was labelled according to a level of RF to be reached in 2100. CCCR2019 focused in particular on RCP2.6 and RCP8.5, which are broadly comparable (but not identical) to SSP1-2.6 and SSP5-8.5. Notably, both SSP1-2.6 and SSP5-8.5 show slightly higher emissions and RF than their equivalent RCP scenarios (Lee et al., 2021).

In general, these illustrative scenarios are all considered to be plausible future pathways, without any assigned probability or likelihood associated with their coming to pass. However, there is evidence that recent emissions have dropped below the higher emissions scenarios, a trend that has been attributed in part to the effect of national climate and land-use policies, as well as declining costs and increasing deployment of renewable energy (Matthews & Wynes, 2022; UNEP, 2023). This is particularly notable for global CO₂ emissions, where the rate of increase of total (fossil fuel + land use) emissions has been slower than that of the no-policies scenarios since 2012 (Figure 3.4). This and other evidence led the IPCC AR6 WGI to assess that the SSP3-7.0 and SSP5-8.5 scenarios represent “counterfactuals that include fewer climate policies compared to ‘business-as-usual’ scenarios – given that ‘business-as-usual’ scenarios could be understood to imply a continuation of existing climate policies,” and that “the likelihood of high-emissions scenarios such as RCP8.5 or SSP5-8.5 is considered low in light of recent developments in the energy sector” (Chen et al., 2021). The evidence also led the IPCC AR6 WGI to assess that “studies that consider possible future emissions trends in the absence of additional climate policies, such as the recent IEA 2020 World Energy Outlook ‘stated policy’ scenario (IEA, 2020), project approximately constant fossil fuel and industrial CO₂ emissions out to 2070, approximately in line with the intermediate RCP4.5, RCP6.0 and SSP2-4.5 scenarios” (Chen et al., 2021). Consistent with this assessment of the evidence, the IPCC WGIII (2022) also shows roughly constant global CO₂ emissions to 2100 based on current policies. This conclusion is further supported by the United Nations Environment Programme’s 2023 and 2024 Emissions Gap Report (UNEP, 2023, 2024), which both project almost constant global greenhouse gas emissions through to 2050 under current adopted and implemented policies (Figure 3.5). Those two projections correspond to an emissions scenario that closely follows emissions in SSP2-4.5.

We acknowledge, however, that the global climate policy landscape is changing rapidly and that projections of the effect of current policies are both highly uncertain and subject to rapid change as national policies are added or removed. The International Energy Agency’s most recent World Energy Outlook (IEA, 2024) also includes a stated policy scenario that projects peak global CO₂ emissions before 2030 followed by an annual decrease of 1% per year through to 2050, resulting in end-of-century warming that is lower than that simulated in SSP2-4.5. These changes are driven largely by the higher stringency of climate policies in China, whose CO₂ emissions decreased by 1.6% in the first quarter of 2025 relative to the previous year (Carbon Brief, 2025a). On the other hand, weakened climate policies in the United States are expected to slow the decline of its emissions substantially, resulting in only a 3% decrease from current levels by 2030 (Carbon Brief, 2025b). The balance of weakened climate policies in the United States against strengthened policy decisions in other high-emitting countries will of course strongly influence forthcoming estimates of the effect of current policies on future emissions.

In addition to the effect of current policies, several studies have estimated what the climate outcome would be if all stated national emissions targets were achieved, which will require the implementation of additional national polices beyond those currently in effect. These studies generally project that global emissions could decline in a manner similar to SSP1-2.6 if all national emissions targets (including those for which implementation is conditional on receiving support from historically higher-emitting countries) are achieved and existing net-zero pledges are also met (IEA, 2024; Meinshausen et al., 2022; UNEP, 2023, 2024). Other recent literature finds that the highest emissions scenarios are less likely, and some literature suggests that the range of scenario uncertainty is smaller (Gillett, 2024; Hausfather & Moore, 2022; Hausfather & Peters, 2020; Huard et al., 2022; Lehner et al., 2023; Moore et al., 2022).

In light of these considerations, we assess that the range of scenario uncertainty centres more closely on lower and moderate future emissions pathways (and away from the highest SSP-based scenario), compared to what was considered in IPCC AR6 (Lee et al., 2021) and in CCCR2019. While plausible future emissions changes remain bracketed by the full range of illustrative SSP-based emissions scenarios, we focus in this chapter on SSP2-4.5 as a scenario representative of current global policies, which leads to global warming of about 2.7°C in 2081–2100 relative to 1850–1900 (Table 3.1). We use SSP1-2.6 as a scenario approximately representative of full implementation of national emissions targets and net-zero pledges, which is approximately consistent with 2°C warming in 2081–2100 relative to 1850–1900. We use SSP3-7.0 as a no-policies scenario, in which global emissions continue to rise throughout this century and global warming reaches 3.6°C in 2081–2100.

It now appears that the highest emissions scenario (SSP5-8.5) would require a substantial weakening of global climate policies, as assessed in 2023 by both the IPCC (2022) and the United Nations Environment Programme (UNEP, 2023). Therefore, in contrast to the framing of future climate in CCCR2019, we do not highlight SSP5-8.5 in the synthesis section above. However, we do acknowledge that this scenario has been used extensively in the climate impacts and adaptation literature to represent a high emissions (strongly warming) world and provide an upper limit for plausible climate-related changes for risk assessment purposes. We also do not highlight the lowest emissions scenario (SSP1-1.9), which is consistent with global warming of close to 1.5°C by the end of the century and would require substantial further strengthening of both climate targets and national policies beyond the current set of national emissions targets and net-zero pledges (Matthews & Wynes, 2022). In particular, wealthy industrialized countries would need to achieve net-zero CO₂ emissions well before 2050 in order to enable global net-zero CO₂ emissions by 2055 (as in SSP1-1.9) (Matthews & Wynes, 2022). However, it is worth noting that Canada’s current target of net-zero greenhouse gas emissions by 2050 (Chapter 1, Box 1.2) implies achieving net-zero CO₂ emissions before 2050. Although Canada has not articulated a separate net-zero target for CO₂ emissions only, achieving net-zero greenhouse gas emissions generally requires that CO₂ emissions reach net zero earlier than all greenhouse gases combined.

Figure take-away: Global greenhouse gas emissions in the intermediate emissions scenario (SSP2-4.5) are approximately consistent with current global climate policies.

Figure title: Greenhouse gas emissions in the SSP-based scenarios versus the range of future emissions assessed in the United Nations Environment Programme’s 2023 Emissions Gap Report

Figure 3.5: Comparison of greenhouse gas emissions, based on their CO₂-equivalent, in the five illustrative SSP-based scenarios assessed in the IPCC AR6 WGI report (2021) (coloured lines), with the current-policies scenario assessed in the United Nations Environment Programme’s Emissions Gap Report (EGR) (2023) (dark grey line). The grey shaded range (EGR range) shows the gap between the effect of current policies and the emissions reductions necessary to limit global warming to about 1.5°C. Note that this plot includes all greenhouse gas emissions (in CO₂-equivalent) through to 2050, rather than only CO₂ emissions, which are shown in Figure 3.4 through to 2100. Source: Gillett (2024).

3.3.2: Climate response

In order to infer future climate change based on a given scenario of changes in greenhouse gas concentrations and other climate change drivers, we need a model of the physical climate system. The climate response uncertainty associated with such models is the second main source of uncertainty in climate projections. This report mainly relies on simulations from the CMIP6 climate models (Eyring et al., 2016; Lee et al., 2021), which are generally newer than the CMIP5 models, which underpinned CCCR2019. Evaluation of the climate simulated by the CMIP6 models for Canada is assessed in Box 3.3. The climate response to increasing greenhouse gas concentrations varies across CMIP6 models, as climate models developed by modelling centres worldwide incorporate various assumptions and representations of physical processes (Zelinka et al., 2020). Differences between models in the simulation of clouds and cloud-related processes that can amplify or dampen the climate response to changes in greenhouse gas concentrations (cloud feedbacks) can explain much of the model differences in climate sensitivity and global warming projections in both CMIP5 and CMIP6 models (Forster et al., 2021).

The best practice for applying climate projections is most often to use multiple climate models, rather than one, in order to capture uncertainties in the climate response (see also Chapter 10, section 10.3.5). However, using multiple models can result in a large uncertainty range for the resulting climate projections. For example, the 5–95% range of Canadian average warming (meaning 90% of model projections lie within this range) under the intermediate emissions scenario (SSP 2-4.5) in the late century (2081–2100), based on an ensemble of 22 models, is 4.1 to 7.8°C (Figure 3.8). Moreover, we do not know how probable it is that the true value of future warming will lie within this ad-hoc range, unless we make further assumptions.

Producing climate projections with narrower and well-calibrated uncertainty ranges is essential for making informed decisions, conducting risk management, and advancing scientific understanding of climate change. Using information from observations of climate change and other observable metrics is one way to do so (Chen et al., 2021). The IPCC AR6 WGI (2021) was the first to use observationally constrained projections of global warming to underpin its assessment of future global warming (Lee et al., 2021). While the IPCC AR6 WGI (2021) did not observationally constrain regional average climate projections, several recent studies demonstrate that uncertainty in regional projections can also be constrained using observations. In section 3.4.2 we assess four approaches to observational constraints and how they have been applied to Canadian temperature projections. In addition, the sea level projections in Chapter 7 were derived using projections of global warming constrained using observations (Fox-Kemper et al., 2021).

For precipitation, not enough literature exists to apply observational constraints, so we use unconstrained climate model output. Observationally constrained estimates of future Canadian warming have narrower uncertainty ranges than, but a similar average warming level to, unconstrained CMIP6 model output (section 3.4). Therefore, using observationally constrained projections of temperature, but unconstrained multi-model CMIP6 projections of other variables, should not introduce any major inconsistencies between projected climate change for different variables.

We use three approaches to observational constraints in section 3.4 to underpin assessed warming projections for Canada as a whole and for regions of Canada. The first method constrains model projections using the properties of each model’s simulated clouds (Y. Liang et al., 2023); the second constrains model projections using past global and regional warming (Li et al., 2025); and the third weights models using their Equilibrium Climate Sensitivity (Cannon, 2024). Both Y. Liang et al. (2023) and Li et al. (2025) demonstrate that their methods work well when used to estimate future warming in one climate model using output from other models. In section 3.4.2, we assess how these methods are applied to constrain Canadian climate projections.

3.3.3: Internal climate variability

The third source of uncertainty in Canadian climate projections is internal climate variability. This refers to natural variations within the climate system that can cause temporary warming or cooling. This is distinct from variations driven by external climate forcings, such as changes in greenhouse gas concentrations, which can cause long-term change (e.g., Deser et al., 2010; Hawkins & Sutton, 2009). Internal variability in Canadian climate is associated in part with climate patterns such as the El Niño–Southern Oscillation (Chapter 4, section 4.8), the Pacific–North American teleconnection pattern (Chapter 4, section 4.8), and the North Atlantic Oscillation (Chapter 4, section 4.3) (Deser et al., 2010). Internal climate variability cannot be predicted more than a few years in advance and therefore represents a source of uncertainty in long-term projections that cannot be reduced. As a result, quantifying internal climate variability is crucial to understanding the fundamental limits of the accuracy of climate model projections. Limits related to internal climate variability would remain even if model development led to climate models that perfectly represented the real climate system and if future forcings were perfectly known (Deser et al., 2012). Internal variability can be quantified using large ensembles of simulations with the same model, run with identical external forcings. The only difference between such ensemble members is that they each start with slightly different initial climate conditions. From these different starting conditions, different “realizations” (simulations) of internal variability are generated. The spread among the ensemble members then approximates the scale of the uncertainty associated with internal variability. For large-enough ensembles (typically consisting of 50 members or more), internal variability is averaged out in the ensemble average. The ensemble average is an approximation of the forced response, that is, the part of the change that is due to external forcings such as greenhouse gas increases from human activities (e.g., Deser et al., 2012). Note that external forcings are not limited to those from human activities but also include natural forcings such as volcanic eruptions and changes in the amount of radiation that the Earth receives from the sun.

The amount of internal variability in most climate variables remains fairly constant as the overall climate changes (Hawkins & Sutton, 2009). This is illustrated for Canadian average temperatures in Figure 3.3 b) and c), where the blue shading represents the effects of internal variability. The relative importance of internal variability compared to both the forced response and the total uncertainty decreases with time, as shown in Figure 3.3 c), with internal variability being relatively more important for projections for the near term than projections for the end of the century (Hawkins & Sutton, 2009).

The importance of internal variability also depends on the location and size of the region of interest (with a larger contribution from internal variability for averages over smaller regions), and on the variable in question (Deser et al., 2012, 2014; Hawkins & Sutton, 2009). This is illustrated in Figure 3.6, which shows winter near-term projections from nine simulations from the Canadian Earth System Model that differ only in their initial conditions. The ensemble average, which approximates the forced climate change, shows more warming in northern Canada than in southern Canada and a general increase in precipitation, consistent with other climate models, such as those used to produce Box 3.1 Figure 1. The large spread between the nine equally plausible realizations of near-term climate change (Figure 3.6) shows that on regional scales, internal variability can have substantial effects. The relative importance of internal variability is substantially larger for precipitation than for surface air temperature, as shown in Figure 3.6, with some ensemble members even showing a decrease in precipitation on Canada’s west coast. This spread is mostly due to the large role of internal variability in projections of winds (Chapter 4, section 4.1, Figure 4.2). In regions where precipitation is affected less by winds and more by temperatures, the effect of internal variability on precipitation is smaller. The large effect of internal variability on precipitation projections for western Canada was also highlighted by Barrow and Sauchyn (2019). The larger role of internal variability on regional scales makes attributing regional climate trends to human influence more challenging than for global average trends.

Figure take-away: Internal climate variability is a source of uncertainty in near-term projections of temperature and precipitation.

Figure title: Effects of internal variability on climate projections

Figure 3.6: Projected near-term (2021–2040) change in winter near-surface temperature in degrees Celsius (°C) and precipitation as a percentage (%) relative to the pre-industrial period (1850–1900). The panels labelled “ensemble mean” represent the average projection from the 50-member CanESM5 large ensemble, while the other panels show simulations from 9 individual members of this ensemble. All projections are driven by an intermediate emissions scenario (SSP2-4.5). Therefore, each individual simulation has the same external forcings but differs in initial conditions.

In contrast to most other climate variables, the internal climate variability of sea ice area does depend on the overall climate. As sea ice thins, year-to-year variability in sea ice area (which is mostly due to internal climate variability) is initially projected to increase, as thinner sea ice melts and refreezes more in response to random variations in temperature. Year-to-year variability in sea ice area is expected to decrease later, when the average sea ice area approaches zero in summer (Kirchmeier-Young et al., 2017; Mioduszewski et al., 2019).

Unlike for long-term climate projections, internal variability can be predicted for some climate variables up to a few years into the future. The most well-known example of such predictions on hourly to daily timescales are weather forecasts, for which physics-based prediction models are initialized with observations to provide skillful predictions of weather up to one to two weeks ahead. Beyond two weeks, the atmosphere becomes too unpredictable because of the exponential growth of initially small changes (known as the “butterfly effect”). However, given the relatively long timescales of processes in the ocean, land, and sea ice, skillful predictions of internal variability in certain climate variables (such as seasonal, annual or multi-year average temperatures) can sometimes be made on timescales of seasons to decades (section 3.4.1).

3.3.4: Confidence terms in key messages: summary of evidence

Key message 3.5: Uncertainties in climate projections result from uncertainties in future emissions of greenhouse gases and other climate change drivers, uncertainties in how the climate system will respond to those changes, and internal climate variability. The range of plausible future global emissions has shifted towards lower emissions scenarios, partly because of developments in global policy and technology (medium confidence). For each emissions scenario, climate response uncertainty has narrowed, owing to improved synthesis of climate models and observations (high confidence). Some internal variability in Canadian climate can now be predicted for periods of up to five years (medium confidence), reducing this source of uncertainty in estimates of near-term climate.

The first sentence of Key Message 3.5 is a statement of fact describing the sources of uncertainty in climate projections. We assess that the range of plausible future global emissions has shifted towards lower emissions scenarios and away from the highest emissions scenarios since the publication of CCCR2019. We assess this with medium confidence based on assessments in IPCC AR6 (Chen et al., 2021) and the United Nations Environment Programme’s 2023 Emissions Gap Report (UNEP, 2023), as well as other recently published literature that points to high emissions scenarios being less probable than they were considered to be at the time of CCCR2019 (section 3.3.1). These assessments are based on developments in global policy and technology, as well as global emissions that have remained below the highest emissions scenarios over the past decade. Furthermore, we note that the inclusion of a very low emissions scenario (SSP1-1.9) in the current set of marker scenarios also suggests that lower emissions scenarios are considered more plausible than was the case at the time of CCCR2019 (when the lowest available emissions scenario was RCP2.6, which is roughly comparable with SSP1-2.6).

We assess with high confidence that climate response uncertainty has narrowed. This is supported by the assessed warming ranges for each scenario in IPCC AR6, which are much narrower than those in the IPCC’s Fifth Assessment Report (AR5) because of the use of observational constraints. It is also supported by recent literature evaluating observational constraints for regional climate projections and applying them to Canadian climate, assessed in section 3.3.2. Our medium confidence that some internal variability in Canadian climate can now be predicted over periods of up to five years is based on the skill measures shown by the World Meteorological Organization (2025) for Canada and other recent literature assessed in sections 3.3.3 and 3.4.1.

3.4: Temperature

Key message 3.6: Average surface air temperature is projected to increase across Canada in all seasons (very high confidence). The projected warming for Canada based on new techniques and climate models is higher than assessed in the first (2019) edition of Canada’s Changing Climate Report for nominally equivalent scenarios (high confidence).

Key message 3.7: Under a current-policies scenario, annual average temperature is projected to increase by 5.0°C (3.8–6.6°C) relative to 1850–1900 by 2081–2100 (high confidence), with larger increases in northern Canada in winter that could exceed 10°C in some regions (medium confidence). Under a no-policies scenario, average warming for Canada is projected to reach 6.9°C (5.2–8.9°C) by the same period (high confidence). Under a net-zero scenario, annual average temperature for Canada is projected to stabilize after 2050, reaching 3.5°C (2.3–4.8°C) above 1850–1900 levels in 2081–2100 (high confidence).

This section assesses both predictions and projections of near-surface temperature over Canada in the coming years. Climate projections are of long-term changes in climate conditions and are typically produced using ensembles of climate model simulations driven by scenarios of changes in climate forcings, such as emissions of greenhouse gases, but not initialized with actual observations of the climate system. Each of the ensemble members have different “realizations” (simulations) of internal climate variability. While the simulated average climate conditions should match observed average climate conditions, the weather on specific days in a climate simulation will not typically match what is actually observed even in the near future. This is because internal climate variability is not synchronized with observations in such climate simulations. By contrast, climate predictions are near-term forecasts of the actual evolution of the climate produced using climate model simulations in which internal climate variability is synchronized with observations. This is done by starting the simulations with the real, observed state of the atmosphere and ocean (similar to how weather forecasts begin). Decadal predictions are climate forecasts of a year to a decade or more. While decadal predictions and climate projections are produced with the same emissions scenarios, decadal predictions can provide more accurate climate information than projections in the first few years of the forecast, as the forecasts start from observations (Lee et al., 2021; WMO, 2025).

3.4.1: Decadal predictions

Decadal predictions are forward-looking forecasts for up to a decade. Their prediction skill is assessed by producing predictions for past decades and comparing these to observed changes over the same period. For Canada, decadal near-surface air temperature predictions have been shown to be most skillful for the eastern part of the country and the Canadian Arctic Archipelago (Delgado-Torres et al., 2022; Doblas-Reyes et al., 2013; Smith et al., 2019; Sospedra-Alfonso et al., 2021; WMO, 2025). The contribution from initialization is partly related to the predictability of the Atlantic Multidecadal Oscillation, a pattern of internal climate variability centred in the North Atlantic, which is described in Chapter 4, section 4.8. Climate model experiments show that changes in the Atlantic Multidecadal Oscillation induce seasonal temperature changes over Canada, with statistically significant warming in the east during the positive phase of the Atlantic Multidecadal Oscillation when the North Atlantic is warmer than normal, and cooling in the west that is more model-dependent (Hodson et al., 2022; Ruprich-Robert et al., 2017). The observed change in the Atlantic Multidecadal Oscillation in the late 1990s appears to have contributed to the long-lead seasonal forecast skill for summer temperature over eastern Canada (Lin et al., 2024) and is also likely to have contributed to the skill of decadal temperature predictions for the region (Smith et al., 2019).

For western Canada, the prediction skill after the first forecast year is generally lower than for eastern Canada. This may be because the Pacific Decadal Oscillation is less predictable (Chapter 4, section 4.8) (Guemas et al., 2012; Kim et al., 2012), and both individual models and multi-model ensembles do not predict it as well. What prediction skill they have is limited to the first few years of their forecasts (Boer & Sospedra-Alfonso, 2019; Choi & Son, 2022).

An example of a recent decadal forecast for Canada is shown in Figure 3.7. This forecast was issued by the World Meteorological Organization, which publishes annual to decadal climate updates every year. These updates show predictions for the next 1 and 5 years based on decadal predictions from 11 international decadal forecasting institutions (WMO, 2025), including the Canadian Centre for Climate Modelling and Analysis, part of Environment and Climate Change Canada. The World Meteorological Organization does not provide initialized predictions beyond five years, as the benefit of initialization drops substantially beyond this time period. Canadian near-surface temperature averaged over 2025–2029 is predicted to be up to 1.5°C warmer in summer than the summer average for 1991–2020. In winter, it is predicted to be up to 1°C warmer in southwestern Canada, and up to 3°C warmer in the Canadian Arctic Archipelago (Figure 3.7). The probability is above 80% everywhere in Canada in both summer and winter that temperatures for 2025–2029 will be warmer than the 1991–2020 averages. There is high confidence in these forecasts for Canada due to the relatively high model skill for predicting near-surface air temperature for summer and, to a lesser degree, winter (WMO, 2025).

Figure take-away: The probability is over 80% for all of Canada that the 2025–2029 average near-surface air temperature will be warmer than the 1991–2020 average.

Figure title: Predictions of Canada’s near-surface air temperature for 2025 to 2029

Figure 3.7: Temperature predictions for extended summer (May to September, top) averaged over 2025 to 2029 and winter (November to March, bottom) averaged over the period from November 2025 to March 2030. The left column shows the near-surface temperature difference from 1991–2020 in degrees Celsius (°C). The right column shows the probability as a percentage (%) that the average near-surface air temperature will be warmer than the corresponding average temperature from 1991–2020. Based on decadal predictions from 11 international institutions, including Environment and Climate Change Canada. Source: World Meteorological Organization (2025).

3.4.2: Projections

CCCR2019 assessed that annual and seasonal average temperatures were projected to increase everywhere in Canada, with much larger changes in northern Canada in winter (X. Zhang et al., 2019). It assessed future changes in Canadian average temperature using CMIP5 climate model simulations, with the 25th and 75th percentiles of the model distribution (representing the middle 50% of the simulated values) reported as a measure of uncertainty. The assessment gave each model simulation equal weight, which means that each model’s projection was counted equally in calculating the multi-model average and the percentiles. CCCR2019 assessed that Canadian average temperatures would increase by 1.8°C (with a 25–75th percentile range of 1.1–2.5°C) by 2081–2100 relative to 1986–2005 under a low emissions scenario (RCP2.6), with temperatures stabilizing at about this level after 2050. This was contrasted with a very high emissions scenario (RCP8.5), in which Canada was projected to warm by 6.3°C (with a 25–75th percentile range of 5.6–7.7°C) by 2081–2100. When these projections are translated to use an 1850–1900 baseline period by adding an observationally constrained estimate of forced warming in 1986–2005 relative to 1850–1900 of 0.9°C (Chapter 2, Box 2.4), these projections correspond to a median estimate Canadian average warming of 2.7°C in 2081–2100 relative to 1850–1900 under RCP2.6, and 7.2°C under RCP8.5. X. Zhang et al. (2019) assessed that stronger warming is projected in the annual average and winter average for the north of Canada. This was due to several factors, including decreases in snow and ice that in turn would lower the albedo (how much light is reflected back to space instead of being absorbed), and more heat transported northward by ocean and air currents. They also assessed that high-latitude amplification of warming is not projected in summer because Arctic Ocean temperatures are constrained to remain close to 0°C. They also projected more winter warming for the east of the country than for the west. A key finding of Chapter 4 of CCCR2019 and of the report as a whole was that Canadian average temperature was projected to rise about twice as fast as the global average temperature, and that this ratio was independent of emissions scenario (X. Zhang et al., 2019).

These projections are consistent with published projections for all of North America. For example, Gutiérrez et al. (2021) assessed that it was virtually certain that annual and seasonal surface temperatures over North America would continue to increase faster than the global average, with greater increases in the far north. Consistent with projections of global average temperature (Lee et al., 2021), Gutiérrez et al. (2021) showed that CMIP6 models on average project somewhat higher warming levels over Northeast North America and Northwest North America, two IPCC-defined regions that together include most of Canada, than do CMIP5 projections for similar scenarios. Sobie et al. (2021) later reached a similar conclusion for Canada. Lee et al. (2021) assessed that about half of the stronger warming in CMIP6 simulations is due to higher average climate sensitivity in those models, and about half is due to higher effective RF (a measure of the radiative imbalance of the Earth due to changes in greenhouse gases and other climate change drivers) in the new nominally equivalent scenarios (for example, in SSP5-8.5 compared to RCP8.5).

A key development in projections of global average temperature in IPCC AR6 relative to IPCC AR5 was the use of observational (or emergent) constraints on projections (Lee et al., 2021). In such approaches, past observations of an observable metric, such as the global warming trend over recent decades, and the relationship between that metric and projected warming across an ensemble of climate models are used to constrain projections of future warming. This relationship is often established, for example, by fitting a straight line to a graph with points representing future warming versus past warming in different climate models. Although based on assumptions about how well models depict the real world, such approaches allow us to estimate the uncertainty in climate projections, and they result in a much narrower range of projected global warming in IPCC AR6 compared to IPCC AR5 for similar scenarios (Lee et al., 2021).

While Lee et al. (2021) assessed that there was not yet enough evidence to apply observational constraints to temperature projections on scales below the global scale, a number of recent studies have applied them on regional scales over Canada (section 3.3.2). In particular, Y. Liang et al. (2023) demonstrated that two metrics associated with global cloud feedbacks performed well at constraining projections of 21st-century warming over Northeast North America and Northwest North America. In a so-called imperfect model test, they evaluated their approach by treating output from each climate model in turn as observations and using their method with output from all other models to predict future warming in that model, and then compared this with the future warming simulated directly in that climate model. They showed that observationally constrained average warming was almost the same as the average CMIP6 warming calculated directly from model output for these regions, but that uncertainty ranges were at least 25% narrower. Li et al. (2025) recently applied the approach of Ribes et al. (2022) to constrain Canadian average temperature projections from CMIP6 simulations using observations of Canadian average temperature and global average temperature. They also showed that this method performed well in an imperfect model test. Cannon (2024) weighted models using an assessed range of Equilibrium Climate Sensitivity to constrain projections of Canadian warming, demonstrating that this method narrowed the projected range of warming for a given emissions scenario, particularly by reducing the upper end of the uncertainty range. Jeong and Cannon (2023) applied an approach to model selection based on a range of regional and global temperature and precipitation metrics. They found that this approach gave a narrower range of projected warming for Canada than the unconstrained CMIP6 ensemble. The results of the approaches used by Li et al. (2025), Y. Liang et al. (2023), and Cannon (2024) are broadly similar, with all three giving a slightly lower average warming, and the methods of Y. Liang et al. (2023) and Cannon (2024) giving much narrower ranges of projected warming, than the raw CMIP6 model output for all three scenarios we consider (Figure 3.8). Jeong and Cannon (2023) also show a narrower range of projected warming for SSP2-4.5, albeit with a slightly higher level of warming than the unconstrained multi-model average for the set of models shown here.

Figure take-away: Three separate observational constraint studies obtained generally narrower and lower ranges of projected warming for Canada than unconstrained multi-model climate projections.

Figure title: Comparison of projected changes in Canada’s average temperature in 2081 to 2100

Figure 3.8: Projected changes in Canada’s annual average temperature in 2081–2100 relative to 1850–1900 under a low emissions scenario (SSP1-2.6), an intermediate emissions scenario (SSP2-4.5) and a high emissions scenario (SSP3-7.0). Grey bars show unconstrained CMIP6 climate model projections and their 5–95% uncertainty ranges (meaning that 90% of projected changes fall within this range), red bars show projections constrained using the approach of Y. Liang et al. (2023), blue bars show projections constrained by Li et al. (2025), purple bars show projections constrained by Cannon (2024), the brown bar shows projections constrained by Jeong and Cannon (2023), and black bars show synthesis 5–95% ranges assessed in this report. Jeong and Cannon (2023) only provided results for SSP2-4.5. We show these for comparison, but do not include them in our assessed range.

Some recent literature suggests that projected warming constrained using past warming trends may be underestimated because internal climate variability in recent decades may have reduced warming in the eastern tropical Pacific over the same period, and in turn reduced observed global warming trends through effects on cloud feedbacks (Armour et al., 2024; Y. Liang et al., 2024). This could influence two of the approaches we assesses here (Cannon, 2024; Li et al., 2025). However, we expect this influence to be limited in our synthesis projections.

In light of the results of these observational-constraint studies and section 3.3.2, we assess that such methods are mature enough to apply to projections of Canadian temperature here. Adopting a similar approach to that used by Lee et al. (2021) for global average projections, we produced synthesis projections by averaging the means and the 5th and 95th percentiles from Li et al. (2025), Y. Liang et al. (2023), and Cannon (2024), resulting in the synthesis ranges shown in Figure 3.8. We assess these 5th–95th percentile ranges as the very likely ranges for projected changes in temperature for Canada under each SSP-based emissions scenario. We use the same approach in the rest of this section to produce projections of average temperature for Canada and subregions of Canada. Given that approaches are less developed for using observational constraints for projected spatial patterns of changes, and that our synthesis Canadian average warming is relatively close to the unconstrained CMIP6 model average (Figure 3.8), we show maps of projected regional changes in temperature based on the unconstrained CMIP6 multi-model average (Figure 3.10).

Figure 3.3a and Table 3.1 show our synthesis of observationally constrained projections of Canadian average warming across the five SSP-based scenarios (section 3.3.1). The projected level of warming is relatively insensitive to emissions scenario until 2040. Over the 2021–2040 period, Canadian average temperature is projected to be 2.7°C (1.8–3.6°C) warmer than in 1850–1900 (Table 3.1).

Warming rates can be important for informing rates of adaptation and were assessed on the global scale in the recent IPCC AR6 (Eyring et al., 2021). We assess the Canadian average warming rate for the near term (2021–2040). The warming rate is somewhat sensitive to scenario over this period, and we focus here on the current-policies scenario (SSP2-4.5) (Figure 3.3a). Li et al. (2025) find a constrained Canadian average warming rate of 0.46°C (0.18 to 0.73°C) per decade for 2021–2040 with SSP2-4.5, while our application of the Y. Liang et al. (2023) approach gives a warming rate of 0.48°C (0.10 to 0.90°C) per decade, and the Cannon (2024) approach gives 0.34°C (-0.03 to 0.74°C) per decade. Averaging these, we project Canadian warming of 0.4°C (0.1–0.8°C) per decade for 2021–2040. This is somewhat less than double the observationally constrained median estimate of the current rate of human-caused global warming of 0.26°C per decade (Forster et al., 2024).

After 2040, projected warming begins to diverge across scenarios (Figure 3.3a). In SSP1-2.6, average temperature in Canada stabilizes in the second half of this century, reaching 3.5°C (2.3–4.8°C) above 1850–1900 levels in 2081–2100 (Table 3.2). This is about 30% more than the warming of 2.7°C assessed by X. Zhang et al. (2019) for the equivalent scenario RCP2.6 (when expressed relative to 1850–1900). A comparison of warming in CMIP5 and CMIP6 simulations indicates that aside from the overall higher level of global warming in the equivalent CMIP6 scenario simulations (Lee et al., 2021), CMIP6 models on average show a slightly stronger amplification of warming over northern North America than the CMIP5 models (Gutiérrez et al., 2021). Canada warms progressively through the century under SSP2-4.5 and higher emissions scenarios, reaching 5.0°C (3.8–6.6°C) warmer in 2081–2100 than in 1850–1900 under SSP2-4.5, and 6.9°C (5.2–8.9°C) warmer under SSP3-7.0 (Table 3.2). Our median estimated warming of 6.9 °C for the high emissions scenario (SSP3-7.0) in 2081–2100 is very close to the 7.2°C assessed by X. Zhang et al. (2019) for the very high emissions scenario RCP8.5. Hence, for comparable scenarios, we obtain a substantially higher projected warming level for Canada than was assessed in CCCR2019. In terms of warming rates, over the final two decades of the century (2081–2100), Canada is projected to still be warming in the high and intermediate scenarios, with a warming trend of 0.8°C (0.2 to 1.2°C) per decade under SSP3-7.0 and 0.3°C (-0.1 to 0.6°C) per decade under SSP2-4.5, while its temperature is projected to stabilize under SSP1-2.6, with a small trend of -0.1°C (-0.4 to 0.2°C) per decade.

As discussed above (Box 3.1), one of the key conclusions of CCCR2019 was that Canadian average warming is projected to be about twice global warming (X. Zhang et al., 2019). The ratio of Canadian average warming to global warming ranges from 2.3 in SSP1-2.6 to 2.0 in SSP5-8.5 using CMIP6, and results are similar using equivalent CMIP5 scenarios (Sobie et al., 2021). Comparing global warming estimates from IPCC AR6 (Table 3.1) (Lee et al., 2021) with our corresponding projections for Canada (Table 3.1) also supports this assessment. Global average temperature is projected to be 1.8°C, 2.7°C, and 3.6°C higher in 2081–2100 than it was in 1850–1900 under SSP1-2.6, SSP2-4.5, and SSP3-7.0, respectively (Lee et al., 2021), while in Canada, the equivalent projections are 3.5°C, 5.0°C, and 6.9°C. We therefore also assess that projected warming in Canada will be about twice global warming. This conclusion is also valid for individual CMIP6 model simulations across scenarios, as shown in Figure 3.9, although some models simulate slightly more than twice the global rate of warming in Canada, and some models simulate slightly less, consistent with the results of Sobie et al. (2021). Canada is projected to warm faster than the global average firstly because land is projected to warm faster than the ocean, and secondly because the high latitudes are projected to warm faster than the lower latitudes (Chapter 2, section 2.4; Chapter 4, section 4.2, FAQ 4.1).

Figure take-away: Canada is projected to warm at about twice the global rate.

Figure title: Relationship between projected Canadian average warming and projected global warming

Figure 3.9: Relationship between Canadian average warming (y-axis) and global warming (x-axis) in degrees Celsius (°C) in CMIP6 simulations under five SSP-based scenarios over the period 2015 to 2100. The dashed grey line corresponds to Canada warming at twice the global rate.

Table 3.1: Projected global and Canadian warming

Changes in global and Canadian average surface temperature relative to 1850–1900 under five SSP-based scenarios, as assessed in the IPCC AR6 WGI report (2021), and as shown in Figure 3.3 and Table 3.2 respectively. Projections are constrained using observations and are an average of results derived using the approaches of Y. Liang et al. (2023), Cannon (2024), and Li et al. (2025), except for SSP1-1.9, which is based on unconstrained projections, due to the small number of models with output available for this scenario. SSP1-1.9 simulations were scaled such that their 1995–2014 average warming matched that of the Y. Liang et al. (2023) constrained projections under SSP2-4.5. The three scenarios highlighted in the synthesis section are shaded blue (SSP1-2.6: net zero, light blue; SSP2-4.5: current policies, blue; SSP3-7.0: no policies; light blue). Note that the differences in projected warming in the near term (2021–2040) across these scenarios are small and may reflect differences in the sets of models used to carry out simulations of the different scenarios.

Consistent with CCCR2019 (X. Zhang et al., 2019), our projections show more warming in the winter than the summer in Canada (Figure 3.10). In the winter and for the annual average, the warming is higher in the north than in the south (see also Chapter 4, section 4.2.3), and in the east than the west. In the summer, the pattern of warming is relatively uniform across the country. A comparison of the pattern of warming projected by CMIP6 models with that from CMIP5 models indicates that as well as the overall higher level of projected warming, the CMIP6 models show a slightly more intensified annual average warming over the Canadian Arctic and the Hudson Bay region (Gutiérrez et al., 2021; Sobie et al., 2021). This differs somewhat from the pattern of annual average warming observed between 1948 and 2023, which was highest in the northwest (Chapter 2, Figure 2.6). Climate models show consistently higher warming levels in eastern Canada than in western Canada at 1°C, 2°C, and 4°C of global warming (IPCC, 2021), so the relatively higher warming level in the northwest than the northeast between 1948 and 2023 was probably associated with internal climate variability. In winter, average warming is projected to exceed 10°C over most of the Arctic Archipelago in the SSP2-4.5 scenario (Figure 3.10). On average, British Columbia is projected to warm the least, although still substantially more than the projected global warming (tables 3.1 and 3.2) (Sobie et al., 2021). The Prairies and Atlantic Canada are projected to warm somewhat more, with warming in Ontario greater still. Quebec is projected to warm even more strongly, at close to the Canadian average rate, while the highest warming level is projected for the North (Table 3.2) (Sobie et al., 2021).

Climate velocities refer to the rate at which climate conditions move on landscape scales, such as warmer climate conditions moving northward. They are calculated as the ratio between a long-term trend in climate conditions (such as warming) and the horizontal gradient in those conditions (Loarie et al., 2009). They differ from the warming rates (°C/decade) presented above because they represent the speed (km/yr) and direction at which climate conditions are moving. Velocities are often used to study the impacts of climate change on species and ecosystems because they approximate how fast organisms will have to move to stay within their suitable climates (Loarie et al., 2009). Velocities tend to be faster in flat, homogeneous regions and slower in mountainous regions, and they may be sensitive to the resolution of the data used to compute them (Brito-Morales et al., 2018). In Canada, estimated annual average air temperature velocities range widely, with faster velocities in northern Canada (Asamoah et al., 2021). In IPCC AR6, observed temperature-based climate velocities from 1970 to 2019 were assessed to be on average 20% slower inside biodiversity hotspots on land and in freshwater environments than outside them, but 69% faster inside marine hotspots (Costello et al., 2022). These results suggest that species in marine biodiversity hotspots may be at particular risk from climate-induced pressures.

Figure take-away: Canada is projected to warm more in the winter than the summer, more in the north than the south, and more in the east than the west.

Figure title: Projected change in temperature across Canada for 2081–2100 relative to 1850–1900 

Figure 3.10: Projected change in temperature across Canada for 2081–2100 relative to 1850–1900 in degrees Celsius (°C) under a low emissions scenario (SSP1-2.6), an intermediate emissions scenario (SSP2-4.5) and a high emissions scenario (SSP3-7.0), based on the CMIP6 multi-model averages. The top row shows the annual average, the middle row shows the average for summer (June to August), and the bottom row shows the average for winter (December to February). Data source: Maps are based on output from 25 CMIP6 models re-gridded onto a 1°×1° grid.

Table 3.2: Projected regional warming in Canada

Projected annual average warming in Canada and regions of Canada in degrees Celsius (°C) in the near term (2021–2040) and late century (2081–2100) relative to the pre-industrial period (1850–1900), under three SSP-based scenarios. Observationally constrained projections and their 5–95% confidence ranges are shown. The projections are based on an average of results using the approaches of Y. Liang et al. (2023), Cannon (2024), and Li et al. (2025). Projections for 2021–2040 are shown for SSP2-4.5 only, but are relatively insensitive to scenario. Projections of Canadian average warming for all five SSP-based scenarios for the near term and late century are shown in Table 3.1.

3.4.3: Confidence terms in key messages: summary of evidence

Key message 3.6: Average surface air temperature is projected to increase across Canada in all seasons (very high confidence). The projected warming for Canada based on new techniques and climate models is higher than assessed in the first (2019) edition of Canada’s Changing Climate Report for nominally equivalent scenarios (high confidence).

Key message 3.7: Under a current-policies scenario, annual average temperature is projected to increase by 5.0°C (3.8–6.6°C) relative to 1850–1900 by 2081–2100 (high confidence), with larger increases in northern Canada in winter that could exceed 10°C in some regions (medium confidence). Under a no-policies scenario, average warming for Canada is projected to reach 6.9°C (5.2–8.9°C) by the same period (high confidence). Under a net-zero scenario, annual average temperature for Canada is projected to stabilize after 2050, reaching 3.5°C (2.3–4.8°C) above 1850–1900 levels in 2081–2100 (high confidence).

Our assessment in Key Message 3.6 that average temperature is projected to increase throughout Canada in all seasons is strongly supported by IPCC AR6 (Gutiérrez et al., 2021), CCCR2019 (X. Zhang et al., 2019), and other relevant literature cited in section 3.4. In IPCC AR6, Gutiérrez et al. (2021) assessed that it is virtually certain that annual and seasonal surface temperatures over all of North America will increase. Our assessment is therefore assigned very high confidence. The higher projected warming level in this assessment than under equivalent scenarios in CCCR2019 (X. Zhang et al., 2019) is based on a comparison between projected warming for 2081–2100 in RCP2.6 and RCP8.5 (X. Zhang et al., 2019), with an adjustment applied to account for the different baseline, and our assessment of warming under SSP1-2.6 and SSP5-8.5, shown in Table 3.1. The latter warming level is substantially higher in both cases. This is a direct comparison of the assessed median estimates of projected warming in the two reports and is therefore assigned high confidence.

The 90% uncertainty ranges for constrained Canadian warming in Key Message 3.7 are the average of results from three different studies (Cannon, 2024; Li et al., 2025; Y. Liang et al., 2023), with two of those studies having verified that their approaches produce uncertainty intervals that are not overconfident in cross-validation tests. By taking the average of the three studies, we are following the approach applied in the IPCC AR6 WGI report (Lee et al., 2021) to global average temperature projections. We therefore have high confidence in these quantitative projections in the first, second, and third sentences of Key Message 3.7.

Our finding that larger increases are projected for the north in winter is a robust conclusion of the analysis in this section, CCCR2019 (X. Zhang et al., 2019), and IPCC AR6 (Gutiérrez et al., 2021). Our assessment that projected warming in winter could exceed 10°C in some regions is based on results shown in Figure 3.10 for average temperature in 2081–2100 under SSP2-4.5 in December–February, where average warming (compared with 1850–1900) exceeds 10°C over most of Nunavut and parts of other provinces and territories. We have medium rather than high confidence because of uncertainties in the regional and seasonal pattern of warming. The assessment of high confidence that annual average temperature for Canada is projected to stabilize after 2050 under the net-zero scenario is based on the time series of projected Canadian average warming for SSP1-2.6 shown in Figure 3.3a, as well as the literature assessed in section 3.4, and the corresponding stabilization of global average temperature over this period as assessed in the IPCC AR6 WGI report (Lee et al., 2021).

3.5: Precipitation

Key message 3.8:

Winter and annual average precipitation are expected to increase everywhere in Canada, especially in northern Canada and around Hudson Bay (high confidence). Summer average precipitation is expected to increase in northern Canada (medium confidence) and decrease in parts of southern Canada (low confidence). Annual average precipitation is projected to increase for Canada as a whole by 10% (7–15%) under a net-zero scenario, 13% (9–18%) under a current-policies scenario, and 17% (12–24%) under a no-policies scenario by 2081–2100 relative to 1850–1900 (medium confidence). Increases in winter precipitation could exceed 50% in parts of Nunavut and Nunavik (northern Quebec) in the current-policies scenario (medium confidence).

Key message 3.9:

Annual snowfall is projected to increase in northern Canada, but it is projected to decrease in southernmost Canada, particularly in coastal regions (medium confidence). This pattern reflects an increase in precipitation everywhere in Canada but warming causing less of it to fall as snow in southernmost regions. Under current-policies and no-policies scenarios, freezing rain is projected to become more frequent over much of Canada, but less frequent over Atlantic Canada and southern Ontario (medium confidence), driven by changes in the simultaneous occurrence of freezing conditions at the surface and warmer air aloft.

This section assesses projected changes in precipitation over Canada. Changes in total precipitation, which represents the sum of rainfall, snowfall, and other forms of precipitation, are assessed in section 3.5.1, changes in snowfall are assessed in section 3.5.2, and changes in freezing rain are assessed in section 3.5.3. Changes in extreme precipitation are assessed in Chapter 8, section 8.3.

3.5.1 Total precipitation

CCCR2019 assessed that winter and annual average precipitation are projected to increase across Canada, but that summer precipitation is projected to decrease in southern Canada under a very high emissions scenario toward the end of the 21st century (X. Zhang et al., 2019). In particular, the report explained that by the end of the century under a very high emissions scenario, small average changes in projected Canadian summer precipitation are the result of large percentage increases in northern Canada offset by large percentage decreases in southern Canada. It also highlighted large projected increases in annual average precipitation of more than 30% for the high Arctic under a very high emissions scenario (RCP8.5).

Gutiérrez et al. (2021) also assessed projected changes in precipitation in Northeast North America and Northwest North America, two IPCC-defined regions that together cover most of Canada. They assessed with very high confidence that these regions will very likely experience increased annual average precipitation, with greater increases at higher levels of warming.

At the time of writing, observational constraints (section 3.3.2) have not been extensively applied to regional precipitation projections for North America, probably because projected precipitation changes are more uncertain and less well correlated with observable metrics. We therefore show unconstrained projections here. We show the 5–95% range across the ensemble of individual simulations as an ad-hoc measure of uncertainty. Note that CCCR2019 showed 25–75% ranges (X. Zhang et al., 2019). In the near term (2021–2040), precipitation increases are insensitive to scenario, and the increase for Canada as a whole relative to 1850–1900 is 7% (5–10%) (Figure 3.11, Table 3.3). Uncertainties are larger for precipitation than for temperature projections.

Figure take-away: Average precipitation in Canada is projected to continue to increase strongly, especially in high emissions scenarios.

Figure title: Projected changes in Canada’s average precipitation under a range of emissions scenarios

Figure 3.11: Projections of percentage (%) changes in Canadian 20-year average precipitation relative to 1850–1900 under five SSP-based scenarios, based on unconstrained CMIP6 simulations. Dotted lines show multi-model means, and shading shows 5–95 percentile ranges of individual model projections. Note that average precipitation in SSP1-1.9 was only available from a subset of models, and these simulations were scaled such that their average change in precipitation between the periods 1850–1900 and 1995–2014 matched that of the models used to simulate SSP2-4.5. The times shown on the x-axis are the central years of each 20-year averaging period.

Table 3.3: Projected changes in annual precipitation for Canada from CMIP6 model simulations

Projected changes in annual average precipitation for Canada and regions of Canada in the near term (2021–2040) and late century (2080–2100) relative to the pre-industrial period (1850–1900) in percent (%), under three SSP-based scenarios. CMIP6 projection averages and 5th–95th percentile ranges of projected changes are shown. Projections for 2021–2040 are shown for SSP2-4.5 only, but are insensitive to scenario.

The pattern of projected changes in precipitation simulated by the CMIP6 models for Canada (Figure 3.12) is generally similar to that simulated by the CMIP5 models assessed in CCCR2019 (X. Zhang et al., 2019), and also broadly consistent with regional climate model projections (Bukovsky & Mearns, 2020). These models simulate the largest absolute increases in precipitation in fall and winter over the Canadian west coast, Quebec and Atlantic Canada (Stewart et al., 2019), and the largest relative increases over the Canadian Arctic Archipelago and Nunavik in the same seasons (X. Zhang et al., 2019) (note that these regions have relatively low average precipitation; see Chapter 2, Supplementary Figure S2.3). The models also simulate weaker increases in precipitation across Canada in spring (Stewart et al., 2019). The CMIP6 models on average simulate decreases in summer precipitation in southernmost Canada at the end of the century under SSP3-7.0, with the largest decreases in the southern parts of British Columbia, Alberta, and Saskatchewan, similar to the behaviour seen in CMIP5 models under RCP8.5 (Stewart et al., 2019; X. Zhang et al., 2019). However, the CMIP6 models show low model agreement in this region (Figure 3.12), and this change is assessed by Lee et al. (2021) as a region of “no or no robust significant change” because fewer than two-thirds of the models’ individual simulations project a change in a 20-year average that is greater than internal climate variability. Hence, there is considerable uncertainty about this projected summer drying. While some global and regional models simulate a decrease in precipitation in southern Canada in summer, others simulate an increase (Bukovsky & Mearns, 2020). Comparing the CMIP5 and CMIP6 projections of changes in precipitation at 2°C and 4°C global warming for Northeast North America and Northwest North America, the CMIP5 and CMIP6 ranges strongly overlap, although on average the CMIP6 models simulate slightly larger increases in precipitation (Gutiérrez et al., 2021). Based on CMIP6 simulations, average projected increases in winter precipitation exceed 50% by the end of the century in much of Nunavut and Nunavik (northern Quebec), even under SSP2-4.5.

Figure take-away: In winter, precipitation is projected to increase strongly across Canada, while in summer it will increase in the north, but could decrease in southernmost Canada with more warming.

Figure title: Projected change in precipitation across Canada for 2081–2100 relative to 1850–1900

Figure 3.12: Projected percentage (%) change in precipitation across Canada for 2081–2100 relative to 1850–1900 under a low emissions scenario (SSP1-2.6), an intermediate emissions scenario (SSP2-4.5) and a high emissions scenario (SSP3-7.0), based on the CMIP6 multi-model averages. The top row shows the annual average, the middle shows the average for summer (June to August), and the bottom shows the average for winter (December to February). Hatching indicates regions where fewer than 80% of the models agree on whether the projected change is positive or negative. Data source: Maps are based on output from 20 CMIP6 models re-gridded onto a 1°×1° grid.

3.5.2 Snowfall

In addition to changes in total precipitation, we assess changes in snowfall. Changes in snowfall are driven by the competing influences of warming (section 3.4) and increases in precipitation. Gutiérrez et al. (2021) assessed that while snow cover would generally decrease across North America over the 21st century, some high-latitude regions would experience an increase due to increased snowfall prevailing over the warming effect. Future changes in snow cover duration and peak snowpack are assessed in Chapter 6, section 6.2.3, which finds that while snow cover duration is projected to be shorter across Canada, peak snowpack is projected to decrease in most regions but increase in the far north, according to CMIP6 model simulations. Projected changes in extreme snowfall are assessed in Chapter 8, section 8.3, which finds increases across most of the country.

Annual snowfall is projected to decrease in southernmost Canada, particularly in southern coastal regions, under all global warming levels (Figure 3.13). However, in contrast to peak snowpack directly simulated by CMIP6 models, which is projected to increase only in Nunavut, and there only slightly (section 6.2.3), annual snowfall is projected to increase in almost all of the Northwest Territories and Nunavut, and most of the Yukon and Nunavik (northern Quebec), based on a snowfall dataset derived from CMIP6 multi-model downscaled and bias-corrected temperature and precipitation (Dai, 2008; Sobie et al., 2024) (Figure 3.13). These increases exceed 25% in parts of northern Nunavut at the 3°C global warming level, which roughly corresponds to projected end-of-century warming under current global climate policies (Table 3.1). One reason why these projections might show a larger area of increases in snowfall than in peak snowpack (Chapter 6, section 6.2.3) is that annual snowfall accumulations do not account for any snowpack losses from direct melt. In addition, CMIP6 winter minimum temperatures tend to be warmer than those observed in most of Canada except Nunavut (Sobie et al., 2021), and correcting this bias is expected to result in a larger region with increasing snowfall relative to the raw model projections. Nonetheless, there is some uncertainty and model sensitivity regarding where exactly the increases will transition to decreases, as indicated by the hatching in Figure 3.13. Overall, we assess with medium confidence that annual snowfall will decrease in southernmost Canada, particularly in coastal regions, while it will increase in northern Canada.

Figure take-away: Snowfall is projected to decrease in southernmost Canada but increase in northern Canada.

Figure title: Projected changes in snowfall across Canada at different global warming levels

Figure 3.13: Projected changes in annual snowfall across Canada at global warming levels of 2°C, 3°C, and 4°C. The left panel shows annual snowfall for a global warming of 1°C, representative of a recent baseline period, and subsequent panels show percentage changes relative to this baseline period for higher global warming levels. Snowfall was estimated from a multi-model, downscaled, bias-corrected daily temperature and precipitation dataset (Sobie et al., 2024). Hatching indicates that fewer than 80% of models agree on whether the projected change will be positive or negative.

3.5.3 Freezing rain

Changes in extreme freezing rain are assessed in Chapter 8, while this section focuses on average changes. Freezing rain and wet snow can stick to structures and installations, with catastrophic consequences (Hanesiak et al., 2022; Roebber & Gyakum, 2003). With more global warming, freezing rain is projected to occur more frequently over most of Canada, especially in the Canadian Prairies and much of northern Canada (Cannon et al., 2020; Jeong et al., 2019; McCray et al., 2022). The duration of freezing rain is projected to increase by more than 5 hours per year for a global warming level of 3°C over much of this region (Figure 3.14), representing more than a 50% increase in many locations (McCray et al., 2022). However, a decrease is projected in southern Ontario and Atlantic Canada, and little change is projected in southern Quebec (Figure 3.14). The increases in freezing rain expected for most of Canada occur because of a melting layer that occurs more often in the (warmer) atmosphere, combined with surface temperatures that are below freezing (Cannon et al., 2020; Jeong et al., 2019; McCray et al., 2022). Projected changes in the occurrence of freezing rain relative to a recent baseline period (1980–2008) are small for 2°C of global warming, but become larger, more widespread, and more consistent across models with increasing warming (Figure 3.14).

Figure take-away: As global warming intensifies, freezing rain is projected to occur more often over much of Canada, but less often in southern Ontario and Atlantic Canada.

Figure title: Projected changes in freezing rain across Canada at different global warming levels

Figure 3.14: Average change in median annual hours of freezing rain relative to the 1980–2009 median at global warming levels of a) 2°C, b) 3°C, and c) 4°C. The averages for 2°C and 3°C are based on an ensemble of four regional climate model simulations for North America, while the average for 4°C is based on an ensemble of two. Results shown are an average of projections using four different algorithms. The dots indicate grid points where 80% of combinations agree on whether change will be positive or negative, while hatching indicates regions where 100% of combinations agree. Source: McCray et al. (2022).

Studies of changes in freezing rain in individual regions reach broadly consistent conclusions using a range of approaches. J. Liang and Sushama (2019) used a regional climate model driven by two global climate models to show that freezing rain associated with atmospheric rivers is projected to occur more often over much of western Canada, especially north of 55°N, because atmospheric rivers will become more frequent and intense (Chapter 4, section 4.5). In a study using regional climate models, Stewart et al. (2019) projected that freezing rain would become more frequent in Nunavut and the Northwest Territories, but would change little in the Prairie provinces. While freezing rain is generally projected to decrease in Atlantic Canada and change little in southern Quebec, local hills and mountains can affect these changes. The topography in the Saint Lawrence River Valley (Marinier et al., 2023) and in the province of New Brunswick (Chartrand et al., 2022) is expected to contribute to maintaining freezing rain in warmer conditions, based on climate simulations that permit convection.

Overall, we assess with medium confidence that freezing rain will become more frequent over much of Canada, particularly in the centre of the country, but less frequent in Atlantic Canada and southern Ontario. Larger changes in the occurrence of freezing rain are projected at higher warming levels.

3.5.4: Confidence terms in key messages: summary of evidence

Key message 3.8:

Winter and annual average precipitation are expected to increase everywhere in Canada, especially in northern Canada and around Hudson Bay (high confidence). Summer average precipitation is expected to increase in northern Canada (medium confidence) and decrease in parts of southern Canada (low confidence). Annual average precipitation is projected to increase for Canada as a whole by 10% (7–15%) under a net-zero scenario, 13% (9–18%) under a current-policies scenario, and 17% (12–24%) under a no-policies scenario by 2081–2100 relative to 1850–1900 (medium confidence). Increases in winter precipitation could exceed 50% in parts of Nunavut and Nunavik (northern Quebec) in the current-policies scenario (medium confidence).

Key message 3.9:

Annual snowfall is projected to increase in northern Canada, but it is projected to decrease in southernmost Canada, particularly in coastal regions (medium confidence). This pattern reflects an increase in precipitation everywhere in Canada but warming causing less of it to fall as snow in southernmost regions. Under current-policies and no-policies scenarios, freezing rain is projected to become more frequent over much of Canada, but less frequent over Atlantic Canada and southern Ontario (medium confidence), driven by changes in the simultaneous occurrence of freezing conditions at the surface and warmer air aloft.

In Key Message 3.8, we assess with high confidence that winter and annual average precipitation are expected to increase everywhere in Canada, especially in northern Canada and around Hudson Bay. This assessment draws on the CMIP6 projections presented in this chapter and the literature assessed in section 3.5, and is similar to the assessment made in CCCR2019 (X. Zhang et al., 2019). Our assessment also draws on the IPCC AR6 (Gutiérrez et al., 2021) assessment that annual average precipitation will very likely increase in Northeast North America and Northwest North America, two IPCC-defined regions that together cover most of Canada. Similarly, our assessment with medium confidence that summer precipitation is expected to increase in northern Canada draws largely from the IPCC AR6 assessment that summer precipitation will likely increase in northern parts of Northeast and Northwest North America (Gutiérrez et al., 2021). It also draws from the CMIP6 projections presented in this chapter, and other recent literature assessed in section 3.5. Our low confidence in projected decreases in summer precipitation in southernmost Canada is based on the IPCC assessment that there is high uncertainty for summer precipitation changes, other than in the far north of North America (Gutiérrez et al., 2021). It is also based on the varying sign of projected precipitation changes in this region across CMIP6 simulations (Figure 3.12) and in the studies assessed in section 3.5. We provide 90% uncertainty ranges for precipitation projections derived directly from the corresponding range of projected changes in the CMIP6 simulations, but since limited literature assesses or constrains precipitation projections for Canada, we have medium confidence in these quantitative projections, as well as in our assessment of regional changes in precipitation in the final sentence of Key Message 3.8. Our assessment that increases in winter precipitation could exceed 50% in Nunavut and Nunavik is based on average projected increases in precipitation exceeding 50% in these regions in Figure 3.12.

In Key Message 3.9, our assessment that annual snowfall is projected to increase in northern Canada is consistent with the IPCC’s assessment (Gutiérrez et al., 2021). Our assessment that snowfall will decrease in southernmost Canada and increase in northern Canada is also consistent with snowpack projections assessed in Chapter 6, section 6.2, and is supported by projections based on Sobie et al. (2024). We have medium rather than high confidence because of the limited number of studies on this topic. There is considerable uncertainty about the extent of the region where snowfall will increase, so we focus on the more confident projected changes in southernmost Canada and northern Canada. The second sentence is a statement of fact about the processes driving changes in snowfall and draws on the literature assessed in section 3.5.2. Our assessment that freezing rain will become more frequent across much of Canada, but less frequent in Atlantic Canada and southern Ontario, is supported by projections of freezing rain from three recent Canada-wide studies (Cannon et al., 2020; Jeong et al., 2019; McCray et al., 2022). We focus on the current-policies and no-policies scenarios because simulated changes in the duration of freezing rain are larger and more statistically significant at the higher levels of warming associated with these scenarios (section 3.5.3). We have medium rather than high confidence in this finding because of the limited coverage of this topic in the IPCC AR6 WGI report or CCCR2019, and because of some differences in projected patterns of change across studies. The final part of the key message is a statement of fact about the processes driving the occurrence of freezing rain and is based on the literature assessed in section 3.5.3.

3.6: Average near-surface wind

Key message 3.10:

Average near-surface wind speed and wind power potential are projected to decrease for Canada (low confidence). Wind speed projections for Canada are highly uncertain due to low model agreement.

This section assesses changes in average near-surface winds over Canada. Projected changes in the large-scale atmospheric circulation, including wind changes over the ocean, are assessed in Chapter 4, sections 4.3 and 4.4. Projected changes in extreme winds over Canada are assessed in Chapter 8, section 8.4.2, which assigns very low confidence to both the direction and magnitude of change of future changes in wind extremes.

In general, climate models project decreases in average near-surface wind speeds over Canada (Karnauskas et al., 2018; Pryor et al., 2020; Ranasinghe et al., 2021 [12.4.6.3]). A decrease in near-surface wind speeds would lower the potential for wind energy generation, as wind power output is highly sensitive to wind speed (e.g., Pryor et al., 2020). These changes have been linked to the increased warming of the Arctic relative to lower latitudes (assessed in Chapter 4, section 4.2), which is thought to reduce the intensity of extratropical storms (Karnauskas et al., 2018). Past changes in near-surface wind speed have also been linked to increases in surface roughness, including urbanization (Chapter 2, section 2.6.2). However, model agreement is generally low. For example, in IPCC AR6 (Ranasinghe et al., 2021), Figure 12.4m shows that there is low model agreement in projections of near-surface wind speed for the low emissions scenario (SSP1-2.6). While Figure 12.4o of that report shows high model agreement for a decrease in wind speed over western Canada in the very high emissions scenario (SSP5-8.5), projections are not shown for the intermediate (SSP2-4.5) or high (SSP3-7.0) emissions scenarios, which we focus on here. The low model agreement over eastern Canada in both scenarios shown by Ranasinghe et al. (2021), and across the country for SSP1-2.6, limits our confidence in projections of average near-surface winds. Confidence in these projections is also limited by the fact that models generally underestimate the strong declines in near-surface winds observed over recent decades (Shen et al., 2022).

3.6.1: Confidence terms in key messages: summary of evidence

Key message 3.10:

Average near-surface wind speed and wind power potential are projected to decrease for Canada (low confidence). Wind speed projections for Canada are highly uncertain due to low model agreement.

The projected decrease in average wind speed is based on multi-model average results in IPCC AR6 (Ranasinghe et al., 2021), but we have low confidence in these projected changes because of low model agreement.

3.7: Key knowledge gaps and emerging issues

For some variables assessed in this chapter, such as future changes in snowfall and wind speed in Canada, limited literature exists. Moreover, while observations are used to constrain projections of Canadian temperature in this chapter, and in the assessment of sea level in Chapter 7, very little literature exists on observationally constrained projections of other variables for Canada. We therefore often have to rely on direct output from the ensemble of available climate model simulations to calculate uncertainty ranges, which may be wider than necessary and not interpretable probabilistically. Another knowledge gap in assessing future climate change for Canada is that for some variables, much literature is focused on very high emissions scenarios, and not on intermediate emissions scenarios such as SSP2-4.5, which are more consistent with current climate policies. Further, even projections based on the full range of SSP-based scenarios only represent a limited set of possible futures, as discussed in section 3.3.1. Many stakeholders’ needs may be better served by more literature making use of comprehensive sets of probabilistic scenarios, such that particular probabilities could be associated with particular scenarios and their associated climate changes. In addition, little literature is available on the extent to which existing scenarios engage with Indigenous worldviews and land rights (Box 3.2). Since these global scenarios represent the possible future evolution of societies, land, and economies, this is a significant knowledge gap in the context of commitments to engage in reconciliation in Canada and elsewhere.

FAQs

FAQ 3.1: What is the difference between climate projections and decadal climate predictions? 

Short answer: 

Climate projections are based on simulations of changes in average climate conditions in response to scenarios of possible future changes in greenhouse gases and other drivers. By contrast, decadal climate predictions start from the observed state of the climate system, like a weather forecast, and can predict year-to-year variations in temperature across Canada for up to a few years.

Long answer: 

Climate projections are usually produced using a set of climate model simulations, which represent the average climate conditions and their long-term changes in response to a scenario of potential future changes in emissions of greenhouse gases and changes in other climate drivers. However, these simulations are not started from actual observations of the atmosphere and ocean. While the average conditions in these simulations should match averaged conditions in the real world, the weather on specific days, months or years in each simulation will not match what is actually observed, even in the near future. Similarly, the sequence of El Niño and La Niña years in these simulations will not match observations. This mismatch is because internal variations are not synchronized with observations in such climate projections.

By contrast, climate predictions are climate model simulations in which internal variability is initially synchronized with observations. This is done by starting the simulations with the real, observed state of the atmosphere and ocean (similar to how weather forecasts begin). Decadal predictions are climate forecasts of several years to a decade or more. While uncertainties increase the further ahead we try to predict, decadal predictions can predict summer and winter average temperature over Canada more accurately than climate projections in the first few years of the forecast. 

FAQ 3.2: What are the main differences between the projections in CCCR2019 and CCCR2026? 

Short answer: 

Overall, since the first edition of Canada’s Changing Climate Report (CCCR2019), our confidence in projections of future climate has increased, and uncertainties have narrowed. In this report (CCCR2026), for a given level of future emissions, we project stronger warming in Canada than was projected in CCCR2019.

Long answer: 

Overall, the projections in this report are consistent with those in CCCR2019, with increased confidence in these projections. However, there are some differences. This report projects stronger warming for Canada than CCCR2019 for comparable scenarios. The median estimate of Canadian warming by 2081–2100 is 0.8°C higher for a low emissions scenario and 1.0°C higher for a very high emissions scenario in this report, compared to that projected in CCCR2019. This is due to differences in the scenarios, updated climate model simulations, and the use of approaches to synthesize information from models and observations to narrow uncertainties in projections. At the same time, the likelihood of the very high emissions scenario, which was one of the two scenarios highlighted in CCCR2019, is now considered to be low.

This report assigns higher confidence to a projected increase in hydrological and agricultural drought in southern Canada than did CCCR2019. Improved understanding of the drivers of past sea level changes has increased our confidence in projections of sea level change in the near term. However, ice-sheet processes remain deeply uncertain and may contribute increased amounts of meltwater to the oceans from the Antarctic ice sheet. Therefore, longer-term sea level projections remain uncertain. 

A headline finding of CCCR2019 was that the Last Ice Area in the Arctic would be north of the Canadian Arctic Archipelago, and that this would be an important refuge for ice-dependent species. In this report, recently observed areas of open water in the region and thinner sea ice has led to an assessment that the sea ice in this region may be less resilient to warming than previously thought. 

Whereas CCCR2019 did not include decadal predictions of climate change describing near-term changes in temperature across Canada, they are included in this report. In addition, CCCR2026 includes projections for many more types of extremes than CCCR2019.

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