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
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.
Earth's Climate
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.
Global Warming
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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