What is climate change?

Recent data has convinced a majority of scientists that important changes to the world's climate are occurring at a much faster rate than what was known in the past. These changes are related to human activity, especially the burning of fossil fuels.

Because of the amplitude and relatively short time in which these changes are occurring, serious impacts on the planet's living systems are predicted.

An ever-changing climate

The Earth's climate has never been constant. Earth's history has been marked by a succession of cold spells (ice ages) and warmer periods. But these changes in the climate have occurred over very long time periods (a few thousand years). The changes we are facing today on the other hand are occurring over a few decades, hence the difficulty for natural systems to adapt to the changes.

Is it getting warmer?

The term climate change is now widely used to express the changes occurring on Earth because the changes are not limited to modifications in the Earth's temperature. It is not to be confused with the term global warming, which refers to the mean increase in Earth's temperature that is presently observed.

It is important to note that the changes in temperature are not similar in different parts of the globe or even in a given country. In Canada for example, different models predict a rise in temperature of up to 5 degrees Celsius before 2100 (Source: Environment Canada) in the most northern areas of the country. In the southern part, and more so on the Atlantic coast, temperature changes will be much less important.

Causes

Earth's climate is a complex system influenced by many factors including the oceans' temperature, ice cover, marine currents, differences in temperature around the globe, etc. But one of the most important factors, essential in controlling the temperature of Earth, is the greenhouse effect. It is a natural phenomenon resulting from the presence of gases in the atmosphere, which prevent some of the earth's heat from escaping into the higher atmosphere and in space. Without this mechanism, the temperature on Earth would be -18 degrees Celsius.

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Of the different greenhouse gases, carbon dioxide (CO2) is the most abundant. Since the beginning of the industrial revolution, humans have been producing more and more of this gas, mostly by the burning of fossil fuels such as oil and coal.

Studies using tools such as ice cores have enabled scientists to estimate that for the past 10 000 years the Earth's atmosphere has contained approximately 280 parts per million (ppm) of CO2 whereas today levels are at 360 ppm (source: Environment Canada) and rising. Because of this rise in CO2 and other greenhouse gases, Earth's climate is changing.

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Signs

The most talked about sign of climate change is that of the general rise in temperature. Different models used by meteorologists give different predictions, but in general, a global temperature rise from 1 to 4 degrees Celsius is predicted in the next century (Source: Environment Canada). This increase in temperature will be much more pronounced in higher latitudes, with increases of up to 5 degrees Celsius in the Canadian Arctic.

Sea level rise, which is the result of ice melting and water expansion because of higher water temperatures, is another sign of climate change. This has been noted all around the globe and predictions are that the level will rise by 50 cm in the next century (Source: Environment Canada).

Another important phenomenon associated with climate change is the increase in extreme weather events, such as storms, winds, storm surges, etc.

Impacts

On the Atlantic coast, effects of climate change are mostly due to the increase in extreme weather events and less to global warming since the warming predicted for the area is less pronounced than in other parts of the country or the globe.

More storms with stronger winds and high precipitation, combined with sea level rise and storm surges, will cause erosion along the coast and certain damages to infrastructures.

Fisheries, forestry and agriculture all risk being impacted by climate change. In our forests for example, a rise in temperature may, on the long term, affect species composition, which will affect our ecosystems and the forest industry. Insects considered pests might also increase in numbers with milder winters predicted with climate change.

Climate change may also have some positive impacts in certain areas. In agriculture for example, warmer weather could permit to grow crops that are presently difficult or not profitable. Unfortunately, on a global perspective, negative impacts of climate change outweigh possible positive impacts.

Other impacts related to climate change are hard to predict. It is hard to predict exactly how important marine currents will be affected by climate change and what will be the impacts of these changes on ocean ecosystems and on fisheries. The coming decades will certainly reveal much more information on these aspects of climate change.

For more information on climate change, visit the following websites:

Freshwater Website:Water and Climate (How might these changes affect Canada?) http://www.ec.gc.ca/water/en/nature/clim/e_canada.htm

Climate change Power Point Presentation http://www.umoncton.ca/ecosage/climatechange.htm

Climate Change - What is Climate Change? http://www.climatechange.gc.ca/english/issues/what_is/index.shtml

cric.ca - Canada's Portal - Quick Guide http://www.cric.ca/en_html/guide/climate/climate_change.html

Climate Change in Canada - What is Climate Change? http://adaptation.nrcan.gc.ca/posters/cc_en.asp

The Green Lane: Climate Change - Overview http://www.ec.gc.ca/climate/overview_what-e.html

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