Kyoto Protocol greenhouse gases and the Canadian Environmental Protection Act: chapter 3

3. Assessment of the Impacts of Climate Change Within the Context of CEPA 1999, Section 64

The material presented in the following sections was selected as being most relevant to Section 64 of CEPA 1999. Even so, the material is to be considered illustrative of the much more extensive body of work contained in the IPCC reports. References to sections in the underlying reports from which material has been extracted are provided for those wishing to read the more comprehensive material.

3.1 Impacts on Natural Systems

The IPCC TAR summary material most relevant to the issue of the impacts of climate change on the Earth's natural systems is listed in the Table below. References to sections of the full WGII report can be found within the Technical Summary references provided. A summary description of the impacts of climate change on natural systems is presented here. More detailed supporting evidence is provided in Tables 1 and 2 in Annex B to this report.

Report Section Ref. Section Heading
WGII Summary for Policymakers 2.1 Recent regional climate changes, particularly temperature increases, have already affected many physical and biological systems
2.3 Natural systems are vulnerable to climate change, and some will be irreversibly damaged.
3.1 (Effects on Vulnerability of) Hydrology and Water Resources
3.3 (Effects on Vulnerability of) Terrestrial and Freshwater Ecosystems
3.4 (Effects on Vulnerability of) Coastal and Marine Ecosystems
4 Vulnerability Varies Across Regions
WGII Technical Summary 4.1 Water Resources
4.3 Terrestrial and Freshwater Ecosystems
4.4 Coastal and Marine Ecosystems
5 Regional Analysis
5.6 North America
5.7 Polar Regions
7.1 Detection of Climate Change Impacts
7.2.1 Unique and Threatened Systems

There is high confidence that the collective evidence supports a conclusion that recent regional changes in temperature have had discernible impacts on many physical and biological systems. Examples of observational changes with linkages to climate change include shrinkage of glaciers; thawing of permafrost; shifts in ice freeze and break-up dates on rivers and lakes; increases in rainfall and rainfall intensity in most mid- and high latitudes of the Northern Hemisphere; lengthening of growing seasons; and earlier flowering dates of trees, emergence of insects, and egg-laying in birds. In about 80% of the biological cases and about 99% of the physical cases the changes are consistent with well-established relationships between temperature and physical and biological processes. The observed changes indicate a sensitivity in these systems to climate changes of a magnitude much smaller than those projected for the coming century.

There is also high confidence that diversity in ecological systems will continue to be affected by climate change and sea-level rise in the future, with an increased risk of extinction for some species currently listed as "critically endangered" and of currently "endangered" or "vulnerable" species becoming even rarer in the 21st century. Recent modeling studies continue to show potential for significant disruption of ecosystems under climate change (high confidence). As a class of ecosystems, inland waters are particularly vulnerable to climate change. Within these systems, the impacts for which there is high or very high confidence include reduction and loss of lake and river ice, loss of habitat for coldwater fish, and increases in extinctions and invasions of exotics. These impacts are of particular relevance to Canada with its large number of inland freshwater ecosystems. Other natural ecosystems at risk include coral reefs, mangroves, and other coastal wetlands; montane ecosystems that are restricted to the upper 200-300 m of mountainous areas; prairie wetlands; remnant native grasslands; ecosystems overlying permafrost; and ice edge ecosystems that provide habitat for polar bears and penguins. Many of these ecosystems at risk exist and occupy large areas within Canada.

The Arctic region is extremely vulnerable to climate change, and major physical and ecological impacts are expected to appear rapidly there as warming in northern high latitudes is expected to be greater than the global average. There will be increasing melting of Arctic glaciers, substantial loss of sea ice, different species compositions on land and sea, poleward shifts in species assemblages, and severe disruptions for communities of people who lead traditional lifestyles.

3.2 Impacts to Systems on which Human Life Depends

The IPCC TAR presents evidence on the impacts of climate change on many different human systems. However, not all of these are equally relevant within the context of CEPA section 64. For the purposes of this discussion, the impacts of climate change that would seem most applicable are:

  1. Impacts on water resources
  2. Impacts on agriculture
  3. Impacts arising from changes in extreme events
  4. Impacts arising from sea level rise
  5. Impacts arising from abrupt climatic and ecological changes

Direct impacts of climate change on water resources and agriculture include changes to precipitation patterns, timing of snowmelt, glacier retreat, evaporation of soil moisture and surface water, and changes in crop yields. In terms of human need, and the needs of other living things, it is not just the availability of food and water that is an issue, but rather access to these resources. Many socio-economic and natural factors will impact on access to adequate supplies of food and clean water but consideration of such issues is beyond the scope of this assessment. Here we will focus on the available evidence for climate change impacts to the production and availability of food and the availability of water.

Changes in extreme events and sea-level rise are arguably the most significant consequences of climate change for humans in the near term. The vulnerability of human societies and ecosystems to climate extremes is demonstrated by the damage, hardship and death caused by events such as droughts, floods, heat waves, avalanches, and storms, hurricanes and cyclones. Often, the impacts from these events fall disproportionately upon the poor. The vulnerability of human settlements along low-lying coastlines to the combined effects of sea-level rise and storm surges is a matter of these settlements, and the coastal resources they depend on, being threatened with flooding, wave damage and permanent inundation.

In the long term, the risk of large-scale, possibly abrupt and potentially irreversible (on human time scales) changes to critical components of the Earth's climate system is of most relevance to the safety and security of life on Earth. Examples of such changes include significant slowing of the thermohaline circulation, which will impact on ocean biochemistry and on climates of the North Atlantic region, large reductions in the Greenland and West Antarctic Ice Sheets, which would lead to global sea level rise measured in metres rather than centimetres; and accelerated global warming resulting from changes to the global carbon cycle with strong positive feedbacks to the climate system (e.g. release of stored carbon from arctic permafrost and release of methane hydrates from ocean sediments). If such changes were to occur, their impacts would be widespread and sustained. Depending on the rate and magnitude of such changes, the capacity for human and natural systems to adapt could be exceeded with substantial impacts resulting.

The IPCC TAR summary material most relevant to the issue of impacts on systems on which human life depends is listed below. References to sections of the full WGII report can be found within the Technical Summary references provided. A summary description of the impacts of climate change on human systems is provided here. More detailed supporting evidence is presented in Tables 3a and b of Annex B.

Report Section Ref. Section Heading
WGII Summary for Policymakers 2.4 Many human systems are sensitive to climate changes, and some are vulnerable.
2.5 Projected changes in climate extremes could have major consequences
2.6 The potential for large-scale and possibly irreversible impacts poses risks that have yet to be reliably quantified.
3.1 (Effects on Vulnerability of) Hydrology and Water Resources
3.2 (Effects on Vulnerability of) Agriculture and Food Security
3.4 (Effects on Vulnerability of) Coastal Zones and Marine Ecosystems
3.6 (Effects on Vulnerability of) Human Settlements, Energy and Industry
4 Vulnerability Varies across Regions
WGII Technical Summary 4.1 Water Resources
4.2 Agriculture and Food Security
4.4 Coastal and Marine Ecosystems
4.5 Human Settlements, Energy and Industry
5 Regional Analysis
5.6 North America
5.7 Polar Regions
7.2 Reasons for Concern
7.2.3 Distribution of Impacts
7.2.4 Extreme Weather Events
7.2.5 Large-scale, Singular Events

A large proportion of the world's population is living under conditions of water scarcity now. Demand for water is generally increasing as a result of population and economic growth. Climate change would exacerbate water shortage and quality problems in many water-scarce areas of the world. Approximately 1.7 billion people, one-third of the world's population, presently live in countries that are water-stressed. This number is projected to increase to approximately 5 billion by 2025 depending on the rate of population growth. It is projected that streamflow and groundwater recharge will be reduced in many parts of the world (medium confidence). The retreat of glaciers has already begun in North America which will affect regional water resources by changing (probably decreasing) water supply from glacial melt during the summer season.

Degradation of soil and water resources is one of the major future challenges for global agriculture. It is established with high confidence that those processes are likely to be intensified by adverse changes in temperature and precipitation. It is established with high confidence also that some crops would benefit from modest warming and increases in CO2 but effects would vary among crops and regions. Some declines will occur due to drought in some areas, including parts of the Canadian Prairies (medium confidence). Overall climate change is likely to tip agriculture production in favour of well-to-do and well-fed regions - which either benefit, under moderate warming, or suffer less severe losses - at the expense of less-well-to-do and less well-fed regions. By the 2080s, the additional number of people at risk of hunger as a result of climate change is estimated to be about 80 million.

The frequency and magnitude of many extreme climate events increase even with a small temperature increase and will become greater at higher temperatures (high confidence). Increases in extreme events can cause critical design or natural thresholds to be exceeded, beyond which the magnitude of impacts increases rapidly (high confidence). The amplitude and frequency of extreme precipitation events is very likely to increase over many areas and the return periods for extreme precipitation events are expected to decrease. This would lead to more frequent floods and landslides with attendant loss of life and other health impacts, property damage, and loss to infrastructure and settlements.

Global mean sea level is projected to rise between 10 and 90 cm by the end of this century. People living in coastal zones will generally be negatively affected by sea-level rise. Highly diverse and productive coastal ecosystems, coastal settlements, and island states will continue to be exposed to pressures whose impacts are expected to be largely negative and potentially disastrous in some instances. Projected sea-level rise will increase the average annual number of people flooded in coastal storm surges (high confidence.) Tens of millions of people living in deltas, in low-lying coastal areas, and on small islands will face risk of displacement.

Greenhouse gas forcing in the 21st century could set in motion large-scale, high impact, non-linear, and potentially abrupt changes in the Earth's physical and biological systems that could have severe consequences at regional or global scales. Although the probabilities of triggering such events are poorly understood they should not be ignored, given the severity of their consequences. Some of these changes have low probability of occurrence during the 21st century; however, greenhouse gas forcing in the 21st century could set in motion changes that could lead to such transitions in subsequent centuries and some of these changes could be irreversible over centuries to millennia.. Events of this type that might be triggered include complete or partial shutdown of the North Atlantic and Antarctic Deep Water formation, disintegration of the West Antarctic and Greenland Ice Sheets, and major perturbations of biosphere-regulated carbon dynamics.

3.3 Impacts on Human Life

The IPCC TAR summary material most relevant to the issue of the impacts of climate change on human life is listed below. References to sections of the full WGII report can be found within the Technical Summary references provided below. A summary description of the impacts of climate change on human life and health is presented, while more detailed supporting evidence is provided in Table 4 of Annex B.

Report Section Section Heading
WGII Summary for Policymakers 2.4 Many human systems are sensitive to climate change and some are vulnerable
2.5 Projected changes in climate extremes could have major consequences
3.5 (Effects on and Vulnerability of) human health
4 Vulnerability varies across regions
WGII Technical Summary 4.5 Human settlements, energy and industry
4.7 Human health
5.6 North America
5.7 Polar Regions

If heat waves increase in frequency and intensity, as they are very likely to do, the risk of death and serious illness would increase, principally in older age groups and the urban poor (high confidence). The greatest increases in thermal stress are forecast for mid- to high-latitude (temperate) cities, especially in populations that have limited resources. The effects of an increase in heat waves often would be exacerbated by increased humidity and urban air pollution. There is medium to high confidence of expansion of areas of potential transmission of malaria and dengue by 2050 to 2100. There is medium confidence that there will be an increase in deaths, injuries, and infections associated with extreme weather such as floods and storms.

In Canada, the projected increased frequency and severity of heat waves may lead to an increase in illness and death, particularly among young, elderly and frail people, especially in large urban areas. Acclimatization may be slower than the rate of ambient temperature change. Vector-borne diseases, including malaria and dengue fever, may expand their ranges in the United States and may develop in Canada.

3.4 Additional Weight-of-Evidence on the Consequences of Climate Change

The impacts described above, and others, were all addressed by the IPCC WGII in their synthesis of the key impacts of climate change into five global Reasons for Concern6. The effort to provide such a synthesis was motivated by the need to provide advice to policymakers on what would constitute "dangerous interference with the climate system" in the context of Article 2 of the United Nations Framework Convention on Climate Change (to which Canada is a signatory). The five Reasons for Concern are:

  1. Risks to unique and threatened systems
  2. Risks from extreme climate events
  3. Distribution of impacts (among people, regions and sectors)
  4. Aggregate (worldwide) impacts
  5. Risks from large-scale discontinuities

Summary conclusions about the impacts of climate change on these Five Reasons for Concern were presented in Box 3-2 of the IPCC Synthesis Report and in Figure SPM-2 of the WGII Summary for Policymakers. These results are reproduced in this report as Table 5 and Figure 1 in Annex B.

The body of evidence regarding climate change impacts on these five Reasons for Concern supported the following conclusion7:

"At a small increase in global mean temperature (0- 2°C)* some of the reasons for concern show the potential for negative impacts, whereas others show little adverse impact or risk. At higher temperature increases, all lines of evidence show a potential for adverse impacts, with impacts in each reason for concern becoming more negative at increasing temperature. There is high confidence in this general relationship between impacts and temperature change, but confidence generally is low in estimates of temperature change thresholds at which different categories of impacts would happen."

* 0-2°C is at the lower end of the projected temperature changes over the next century. [WGI Technical Summary Section F: The Projections of the Earth's Future Climate]

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