Frequently asked questions about climate change

Climate change is a long-term shift in weather conditions measured by changes in temperature, precipitation, wind, snow cover, and other indicators. It can involve both changes in average conditions and changes in variability, including, for example, changes in extreme conditions. Climate change can be caused by natural processes, such as changes in the output of the sun and in the amount of volcanic dust in the atmosphere. It can also be affected by human activities. In particular, human activities that involve burning fossil fuels (eg. coal, oil) can change the composition of the atmosphere through emissions of greenhouse gases and other substances. The build-up of greenhouse gases in the atmosphere is the primary cause for concern about climate change now and into the immediate future.

Air pollution is made of various chemicals and particles that contaminate the atmosphere around the earth. Clean air issues, such as smog and acid rain, primarily influence the lowest part of the atmosphere, which is also the zone of air we breathe. Clean air is compromised by air pollutants that come from a variety of sources such as industries and our vehicles. Air pollution can have significant direct and indirect impacts on our health, the environment, and the economy. These impacts may be experienced near the source of the pollution, but some pollutants can also be transformed and transported great distances by the wind before falling back to the ground, water, or land within our communities. Many air pollutants also play a role in the earth's radiation balance and so contribute to climate change.

Greenhouse gases refer to gases in the atmosphere that absorb heat radiated from earth. Together, greenhouse gases act like a blanket reducing heat loss, similar to the way the glass of a greenhouse warms the air inside the greenhouse. This greenhouse effect is a natural phenomenon that creates warmer conditions on Earth and makes life, as we know it, possible. Concentrations of greenhouse gases in the atmosphere have grown significantly since pre-industrial times largely because of the burning of fossil fuels and permanent forest loss. The rise in greenhouse gas concentrations is amplifying the natural greenhouse effect and warming the planet, affecting wind patterns, precipitation, and storm events.

The International Panel on Climate Change (IPCC) is a scientific, interdisciplinary body that was established in 1988 by the World Meteorological Association (WMO) and the United Nations Environment Program (UNEP). It provides decision-makers and others with an objective source of information about climate change. Its role is to assess the latest scientific, technical, and socio-economic literature produced worldwide relevant to understanding the risk of human-induced climate change, its observed and projected impacts, and options for adaptation and mitigation.

The IPCC regularly publishes its findings in assessment reports that are reviewed by experts and governments from around the world.

See how the Government of Canada is helping Canadians adapt.

Climate change refers to a long-term shift in weather conditions, including temperature, precipitation, winds, and other indicators. This may vary from region to region. For example, temperature increases will vary from one region to another, and precipitation may increase in some regions but decrease in other regions. Global warming refers specifically to an increase in the global average surface temperature. Global warming is an indicator of climate change. It is often misunderstood to imply that the world will warm uniformly. In fact, some areas of the world will warm more, while others will warm less than the global average. Natural variability, year-to-year, decade-to-decade, is superimposed on this long-term change.

The greenhouse effect describes the way that the atmosphere insulates the planet from heat loss.  The atmosphere is largely transparent to sunlight, allowing most sunlight to pass through the atmosphere to heat the planet. However, small concentrations of “greenhouse gases” in the atmosphere absorb much of the outgoing heat energy radiated by the earth itself, and return much of this energy back towards the surface. This process keeps the surface much warmer than if the greenhouse gases were absent. This process is referred to as the greenhouse effect because it resembles the role of glass in a greenhouse, creating warmer conditions than would otherwise occur.

Changes in climate can be caused by natural events and processes and by human influences. However, since the Industrial Revolution, climate change due to human influences has increased significantly. Key human influences include changes in greenhouse gas concentrations and alterations in land use. These influences both affect the amount of heat energy escaping to space, and change the amount of sunlight reflected to space. The overall effect of these activities since the Industrial Revolution has been a warming effect.  The build-up of greenhouse gases in the atmosphere is the primary cause for concern about climate change over the coming century. Key natural factors that can influence climate change on century time scales include changes in the intensity of sunlight reaching the earth and in the concentration of volcanic dust in the atmosphere. Both of these factors alter the amount of sunlight that is absorbed by the earth's climate system. The influence of solar irradiance changes and volcanic eruptions since the Industrial Revolution has been very small relative to the influence of human emissions of greenhouse gases. These relative influences are expected to hold true for the coming centuries as well.

The burning of fossil fuels - primarily coal, oil, and natural gas - currently accounts for between 70-90 % of all human emissions of carbon dioxide, which is a major greenhouse gas. Fossil fuels are used for transportation, manufacturing, heating, cooling, electricity generation, and other applications. The remainder of the carbon dioxide emissions comes from human land use activities such as ranching, agriculture, and the clearing and degradation of forests. Other primary sources of greenhouse gases include the production and transport of fossil fuels, agricultural activities, waste management, and industrial processes.

Many of the most costly impacts of climate change--in terms of both life and property--will result from more frequent, longer-lasting, or more intense extreme weather events and associated natural disasters, such as heavy precipitation events, floods, heat waves, droughts, and wildfires. Projecting how the risk of such events may change in the future is challenging and the answer will be different for different regions of the world and for different regions of Canada, and will depend on the type of extreme event in question. That said, a shift in average conditions to a warmer climate is expected, based on physical reasoning, to be accompanied by a shift in extreme temperature conditions, with increases in hot extremes and decreases in cold extremes. Also, a warmer atmosphere will hold more moisture, which means that when it does rain or snow, more water will be available to fall. Precipitation is therefore projected to be concentrated into more intense events, with periods of little precipitation in between. Somewhat counter-intuitively then, more frequent heavy precipitation events in the future are expected to be accompanied by longer dry periods in between.

A warming climate in Canada will have impacts on water quantity across the country. For example, for the Great Lakes basin, the majority of climate model simulations project decreases in lake levels. The Prairies, Canada’s major dryland area, are projected to experience drier conditions in the future, with lower summer streamflows, falling lake levels, retreating glaciers, and increasing soil - and surface - water deficits. In some areas, more frequent heavy downpours may cause localized flooding and overwhelm current sewage treatment facilities with increased volumes of stormwater and sewage runoff. Across Canada, there is concern that water resources will come under increasing pressure and could become seasonally scarce as a result of regional changes in water supply (from changes to precipitation, snow, and glacier melt), increasing evapotranspiration with warmer temperatures, and increasing demands from a range of activities.

Scientific projections indicate that climate change could affect the health and well-being of Canadians in a number of ways. A few of these predicted results include: increased smog and heat waves resulting in more temperature-related illness and death; the spread of infectious diseases such as malaria‚ dengue and yellow fever into Canada as insects carrying these diseases migrate northward with the warming climate; and the quality and the quantity of drinking water could decline as water sources in some areas become threatened by drought.

Carbon dioxide is the main cause of human-induced climate change. It is a very long-lived gas which means levels of carbon dioxide build up in the atmosphere with ongoing human emissions. Stopping climate change, that is, stabilizing global average temperature, can only be brought about by reducing global emissions of carbon dioxide from human fossil fuel combustion and industrial processes to near-zero levels. Climate models have shown that to have a good (greater than 2/3) chance of limiting global warming to 2 °C, this ‘zeroing’ of human emissions needs to be accomplished sometime in the second half of the century. This indicates how difficult the challenge is.

The UNFCCC is an international treaty that sets out an overall framework for intergovernmental efforts to tackle the challenges posed by climate change.  The Convention’s ultimate objective is to stabilize atmospheric concentrations of greenhouse gases at a level that would prevent dangerous human interference with the climate system.

The Convention, which entered into force on March 21, 1994, has near universal membership, with 195 ratifying Parties (194 countries and one regional organization, the European Union).

Under the Convention, governments:

• Gather and share information on greenhouse gas emissions, national policies and best practices;
• Launch national strategies for addressing greenhouse gas emissions and adapting to expected impacts, including the provision of financial and technological support to developing countries ; and
• Cooperate in adapting to the negative impacts of climate change.

For more information, visit the UNFCCC website.

The COP stands for the Conference of the Parties. The COP is the supreme body of the UNFCCC. It currently meets once a year to review the Convention's progress and establish the rules of its implementation.

The United Nations Climate Change meetings are open to Parties to the UNFCCC, observer states, United Nations bodies and agencies, and non-governmental organizations that have been formally admitted as observers. Accredited media can also attend.

Since the UNFCCC entered into force in 1994, Canada has participated in at each of its sessions to discuss ways to address the global challenge of climate change, and to take stock of national and international progress to effectively reduce greenhouse gas emissions.

Notably, government officials represent Canada’s interests and contribute their expertise on various climate change issues with the view of establishing a fair, environmentally effective and comprehensive global climate change regime.

Under the Convention, Canada is required to:

• Provide data on greenhouse gas emissions on an annual basis;
• Submit national communications periodically, reporting on progress in reducing its net greenhouse gas emissions;
• Enact policies and measures to address greenhouse gases;
• Provide financial and technological resources to developing country Parties to help them address climate change; and
• Conduct systematic observations of the climate system and research on climate change and its impacts.