Canada and Climate Change
Climate change is a reality, and Canadians are increasingly concerned with how their country - with its rich but not inexhaustible natural resources - will both impact and be affected by the global climate change that has become a pressing issue. But to understand what scientists, politicians and others mean when they speak of "climate change" and "global warming" some basic background information is necessary, such as how the earth maintains a climate in the first place and what natural processes are at work, which affect the earth's temperature.
Earth's atmosphere is a layer of gases that surrounds our planet and is kept in place by the Earth's gravity. This mixture of gases is roughly 78% nitrogen, 21% oxygen, 0.93% argon, 0.04% carbon dioxide, and trace amounts of other gases, in addition to water vapor. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.
Climate is the sum of weather conditions existing over a period of time--a month, a decade, a century or longer--and climate change results from a complex process that scientists are only beginning to understand. Our climate has been constantly changing since the Earth began, with periods of global warming and global cooling long before human beings (and their various activities) came on the scene. The natural global warming and cooling that has occurred in the past can offer useful insights into present processes.
The Greenhouse Effect
The Earth receives energy from the Sun in the form of radiation. Much of that radiation doesn't get past our atmosphere, but that which does is responsible for heating up the Earth. As the Earth warms up, it in turn emits Infrared radiation (IR) back into space. Now if it simply sent it all back, we'd be in trouble (and a lot colder). But actually what happens is that "greenhouse gases" in our atmosphere absorb the thermal radiation emitted by the Earth's surface and send the energy back to the Earth's surface, warming it to the relatively comfortable temperatures that we have now. Without this recycling of energy by greenhouse gases in the atmosphere, the Earth would be about 30 degrees Celsius cooler than it is now.
Averaged over all land and ocean surfaces, temperatures on Earth have warmed about 1.35°F (0.75ºC) over the last century. Much of this warming has occurred since 1979. Global warming is thus the observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades and its projected continuation. Models referenced by the Intergovernmental Panel on Climate Change (IPCC) predict that global temperatures are likely to increase by 1.1 to 6.4 °C (2.0 to 11.5 °F) between 1990 and 2100. This relatively small change in temperature may seem unremarkable or even insignificant, but in actuality it doesn't take much to make an impact (think of how an increase of a few degrees in human body temperature can lead to fever and serious repercussions if the temperature rise goes unchecked). Even a change of less than one degree Celsius is enough to cause changes in weather patterns, rainfall and sea levels.
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