The Science of Climate Change

Our climate is changing more rapidly than it has at any other time in the past 1 000 years. Scientists predict that the global average temperature will rise by 1.4-5.8°C by the end of the 21st century, and that Canada could see an increase greater than that. Such drastic warming will affect many other aspects of the weather, including wind patterns, precipitation, and severe weather events, creating serious consequences for humanity and the global environment.

The primary cause of climate change is the emission of greenhouse gases. Some of these, such as carbon dioxide and nitrous oxide, are produced through the burning of fossil fuels, wood and coal, while others, such as methane and halocarbons (e.g., chlorofluorocarbons and hydrochlorofluorocarbons) result from other human activities. These gases remain in the atmosphere for long periods of time, absorbing heat and radiating it back to the earth's surface—instead of allowing it to pass through into space.

As one of the parties to the United Nations Framework Convention on Climate Change, Canada is working to reduce its greenhouse-gas emissions to six per cent below 1990 levels by 2008-12. Last October, the Government of Canada released its $500-million Action Plan 2000 —a strategy that focuses on key sectors and includes initiatives in transportation, energy, industry, buildings, forestry and agriculture, international projects, and science and technology. Combined with funding from Budget 2000, this brings the federal investment in tackling the threat of climate change to more than $1.1 billion. When it is fully implemented, Action Plan 2000 will help move Canada one-third of the way toward meeting this goal of emission reduction. Subsequent plans, as well as actions by provinces, territories and industry, will bring it even closer.

Decision makers require scientific information in order to negotiate Canada's international position on climate change, and to determine appropriate ways to address the issue domestically. Much of this information comes from scientists in Environment Canada's Meteorological Service of Canada (MSC), who conduct research into the key processes of our climate system, monitor and assess the current state of the climate and the factors that influence it, and develop models to predict future conditions. They also study the impacts of climate change on natural and socioeconomic systems, and the ability of Canadian communities to adapt.

Such research shows that our climate system is a complex balancing act involving the sun, atmosphere, oceans and land. Solar radiation heats the earth and provides the energy that drives atmospheric circulation. The atmosphere screens out the sun's harmful rays and acts as a storehouse for various gases and particles. Both air circulation patterns and the make-up of the atmosphere have a major influence on climate and weather systems. Ocean currents and atmospheric circulation patterns help to moderate high-latitude climates, such as Canada's, by transferring heat from the tropics toward the cooler poles. Other forms of water—from water vapour and precipitation to snow, sea-ice and the ice caps—also have an effect. Continents and their features absorb or reflect the sun's energy and affect air currents.

Humans have altered many different aspects of this climate system through economic and social development. To determine the impact these changes have had, scientists study data from historical instrumental and proxy records—such as tree rings, ice cores taken from ice caps, coral records, and sediment cores taken from lake and sea beds—to extend the climate record back as far as several thousands of years. These data are augmented by measurements of the current climate taken by volunteer and professional observers at hundreds of locations across the country. The resulting information is crucial for detecting climate change and making the link between changes and anthropogenic factors.

Canadian scientists are involved in several international efforts to help strengthen this link, among them the World Climate Research Programme. Canada's efforts under the program include ground-based measurements of surface radiation to help determine how much energy is entering and leaving the earth's atmosphere, studying ocean processes to improve global climate models, and the development and application of comprehensive regional and global climate models. Another major contribution is a study of water and energy cycles in the permafrost-saturated and largely snow-covered lands of the Mackenzie River Basin as part of the Global Energy and Water Experiment. This experiment will help improve understanding of cold regions and high-latitude hydrological and meteorological processes, and the role they play in the global climate system.

Since the primary influence on climate change has been changes to the chemical composition of the atmosphere, the study of greenhouse gases and their natural cycles has been an area of increasing focus for scientists. Of particular interest is determining how much of the carbon contained in emitted greenhouse gases ends up in natural "sinks" in our oceans, forests, soil and wetlands. In addition to taking regular measurements of greenhouse-gas concentrations in the Arctic, on the east and west coasts, and in the Pacific Ocean, MSC researchers also participate in major field programs, including a collaborative project examining greenhouse-gas fluctuations and carbon sequestration in the boreal forest.

Projected change in surface temperature around the world between 1980 and 2050. This projection was generated by the Meteorological Service of Canada's second-generation global coupled climate model when forced with a widely used scenario of future emissions. The darker the shading, the greater the projected change.

All of this information contributes to the creation of global climate models—powerful computer simulators that use complex mathematical approximations of the physical and, to some extent, biological and chemical processes that underlie the global climate system. Researchers at MSC's Canadian Centre for Climate Modelling and Analysis (CCCma) in Victoria, British Columbia, develop and use one of the world's most sophisticated coupled climate models, incorporating interacting atmospheric, land, ocean and sea-ice components, to study the mechanisms of climate variability and change and to make projections of future climate.

The Centre recently modelled the effects of an increase in greenhouse gas and aerosol concentrations from 1850 to 2100 using MSC's supercomputer in Dorval, Quebec. The result of this extensive computing effort shows a strong correlation with past trends determined from historical and proxy records. It predicts that global warming and other effects of climate change over the next century will be greatest over land and at high altitudes, and that there will be an increase in global precipitation and a decrease in sea-ice and snow.

To bring together the many kinds of expertise required to develop and enhance global coupled climate models such as this, the Centre has collaborated with nine research groups in 18 Canadian universities and government labs in the Canadian Climate Research Network over the past six years. An important aspect of the Network's efforts has been to embed regional climate models in the CCCma's global coupled model, so that more precise projections of climate change can be made on regional scales. In addition, Network research groups have worked to improve the representation of oceanic and sea-ice processes, clouds and radiation, stratospheric chemistry, and the land surface.

Projections of future climate are used by scientists for climate impact studies, and to formulate strategies for responding to climate change. Selected data from Canadian simulations have been provided to the Intergovernmental Panel on Climate Change for use in its global climate change assessment reports. Environment Canada scientists were lead authors, contributors and reviewers of the first two reports, and are participating in the production of the third report, which will be completed by the middle of this year. The Canadian model was also used in a national assessment of the potential impacts of climate variability and change in the United States. Results from the CCCma model are available on- line at http://www.cccma.bc.ec.gc.ca/eng_index.html.

The U.S. assessment incorporated many features of the Canada Country Study, in which Environment Canada worked with more than 55 experts from across Canada to survey and synthesize research on the social, biological and economic impacts of climate change. The study revealed a variety of far-reaching effects, including: earlier harvests and a greater risk of pests and disease for grain crops; the movement of forests and forest species further north and to higher altitudes; more illnesses and deaths from the increased frequency and severity of heatwaves and smog episodes; the possible migration of sub-tropical diseases northward; and threats to freshwater and wetland species and habitat due to decreases in lake and groundwater levels.

A similar effort is currently being carried out on a more regional scale, as MSC scientists strive to incorporate climate change impacts into the Georgia Basin Quest computer simulation program. The program will enable people to see the impacts their activities —including the production of fossil fuels—will have on water resources, agriculture, forestry, fisheries and air quality in the future. Other ongoing projects include the examination of the potential impacts of climate change in national parks, appraisals of the costs and benefits of climate-change impacts, and the development of adaptation options for various sectors.

Continued investment in research, both within government and the university sector, is key to improving our knowledge of how the different components of the climate system interact, creating more advanced models, and sharpening our predictive capabilities. It is through this research that we will be better able to minimize human impacts on climate, and better equipped to adapt to these changes.

  Home |  Air |  Atmospheric Science |  Climate Change |  Environmental Action |  Habitat |  Pollution |  Species at Risk |  Technology |  Water |  Weather |  Wildlife