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As the likelihood of climate change resulting from human activities increases, there is a growing need to estimate the magnitude of these changes, determine their impacts on the environment, our society and our economy, and identify the most effective strategies for adapting to the anticipated changes. This report summarizes the most recent literature describing the impacts of current climate and the potential effects of anticipated climate change on the environment and on those social and economic sectors in Ontario most likely to undergo significant changes.

Current Climate of Ontario

Ontario's climate varies widely from season to season and from one part of the province to another. In Northern Ontario, the climate is primarily continental, with cold winters and mild summers. Most precipitation falls in the form of summer showers and thunderstorms; winter snowfall amounts can be impressive, but usually contain less water. Precipitation amounts increase as one moves from northwest to southeast - a reflection of the increasing influence of moisture transported from the Great Lakes and the Gulf of Mexico. In Southern Ontario, the climate is highly modified by the influence of the Great Lakes. The addition of moisture from the Great Lakes in autumn and winter increases precipitation amounts, while the heat of the Great Lakes protects the region from the worst of winter's cold. In the spring and summer, the cooler waters of the Great Lakes act to moderate the oppressive heat of tropical air, which regularly approaches the area. The combination of uniform precipitation amounts year-round, delayed spring and autumn, and moderated temperatures in winter and summer makes Southern Ontario's climate one of the most suitable in Canada for both agriculture and human settlement.

Ontario experiences a variety of extreme weather events. In winter, Northern Ontario can have prolonged periods of extreme cold. Farther south, very heavy snow is a regular feature in the snowbelts to the lee of Lakes Superior and Huron, and Georgian Bay; major storms lash most parts of Ontario at least once or twice per year, with high winds and a mix of rain, freezing rain and snow. In spring, rapid snowmelt or ice jamming can lead to flooding of Ontario's rivers. Spring also marks the beginning of the tornado season in Southern Ontario, which has the highest frequency of tornadoes in Canada. In summer, thunderstorms can produce heavy downpours, hail, damaging winds and occasional tornadoes. Stagnant tropical air masses can bring poor air quality, heat waves and drought. In autumn, an early frost can damage crops, and remnants of hurricanes occasionally produce high winds and excessive rainfalls.

Impacts of Climate

Ontario's environment, society and economy are all affected by climate. The environment is well adapted to the current climate. Our economy and society have also adjusted, but as our knowledge of climate expands and our awareness of its impacts increases, further improvement is possible. The social and economic sectors most affected by climate include water resources, human health, the built environment, energy, transportation, tourism and recreation, forestry, agriculture, construction and finance. Some of the most significant impacts are listed below.

Future Climate of Ontario

For Ontario, results from some of the latest Global Circulation Model (GCM) simulations of climate, with an atmosphere containing twice the current amount of greenhouse gases, suggest an average annual warming of some 2° to 5°C by the latter part of the 21st century. Even if greenhouse gas amounts stabilize at that point, temperatures would continue to increase thereafter, with overall warming of 3° to 8°C possible. Increases will probably be greater in the winter than in the summer. These changes would significantly decrease the duration of the annual snow season and lengthen the growing season. They could increase the frequency and severity of extreme heat events in summer. It must be remembered, however, that even the most sophisticated GCMs do not incorporate the effects of important local climate controls, such as the Great Lakes. For this and other reasons, considerable uncertainty still exists about the application of GCM results on a regional scale.

Anticipated Impacts of Future Climate

While the greatest confidence is attached to projections of changes in temperatures, the most significant impacts are expected to result from the changes in other climatic conditions. These include changes in precipitation patterns, in soil moisture, and possibly in the frequency and intensity of severe weather events. Some of the key impacts of a changing climate are listed here.

Adaptation to Climate Variability and Change

As we have seen, many aspects of Ontario's environment, economy and society are sensitive to climate variability and anticipated changes in climate conditions. One way Ontario could lessen the impacts of a changing climate is to reduce known vulnerabilities to current climate variability. In some cases, a changing climate could necessitate additional adaptive actions. Some adaptive strategies for climate sensitive sectors are suggested here.

Areas Requiring Further Research

Information regarding climate change impacts, especially on regional scales, is still somewhat inexact. Although much more is known about the impacts of current climate variability, there remain gaps in our knowledge in this area, too. In order to better assess the relative magnitudes of climate impacts, and devise effective adaptation strategies, more research is required in all areas. Some of the key areas for future study are:

Accessible, high-quality environmental and socio-economic data is a requisite in order to detect climate change, to understand climate impacts, and to formulate and execute effective adaptation strategies.

Concluding Remarks

Adapting most effectively to a changing climate requires a knowledge of how climate will change and how the changes will affect the environment, society and the economy. However, changes in other key variables, such as technology, personal preferences and social values, will probably influence both the rate of climate change and our ability to adapt to it. For this reason, the unforeseeable future, the most prudent strategies to adopt today are so-called "no regrets" strategies. That is, regardless of what changes occur, these strategies will provide a net benefit to the environment, society and the economy. Examples of no-regrets strategies include more efficient use of energy and materials, and improving adaptation to current climate.

For Ontario, a changing climate will present challenges for some sectors, and opportunities for others. The present technology of climate prediction and our knowledge of climate impacts do not allow us to make confident estimates of losses and benefits. However, most expert opinion suggests that climate will continue to change, and that the costs of the impacts are likely to exceed the benefits from a warmer climate. Therefore, a sensible approach would be to: minimize anthropogenic forcing of climate change to the extent possible, without unduly disrupting the very environmental, social and economic systems we seek to preserve; and to improve our adaptation to current climate conditions in ways that will increase our ability to adjust to future changes.

The responsibility for action is broadly based: the scientific community must provide advice and information; governments must identify and eliminate barriers and disincentives to adaptation; and those in affected sectors must educate themselves about the risks and opportunities of a changing climate and act accordingly.

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Environment Canada By: Teresa Gamble, December 22, 1997
URL: http://www.on.ec.gc.ca/canada-country-study/intro.html
Copyright © 1997, Environment Canada. All rights reserved.
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