INDEPTH: CLIMATE CHANGE
Global warming
CBC News Online | March 24, 2005
Switch on the TV or radio these days, and you'll learn about icebergs melting and be bombarded with ads for movies depicting catastrophic weather disasters.
A hundred years ago, the phrase "climate change" would not likely have set anyone's spine tingling, but today it has become fodder for the latest thrillers and disaster scenarios. The reality is likely to be less sudden, but possibly no less dramatic.
How it works
Global warming is the increase over time of the Earth's average surface temperature. Although the term "global warming" may conjure up images of coal-fired plants and yuppies in SUVs, the climate of the Earth has always been in flux, including periods of sustained warming and cooling.
In general it works like this: the sun shines on the Earth. Most of those rays pass through the Earth's atmosphere, although some are reflected back into space. The surface of the Earth absorbs the energy. Some of that heat energy is re-emitted. The heat reflected from the surface travels back up into the atmosphere.
There, it can be absorbed by the gases commonly known as greenhouse gases. These are naturally occurring gases as well as those from burning fossil fuels; they trap the heat, warming up the Earth's surface even more. Without naturally-occurring greenhouse gases, the Earth would be about 33 degrees Celsius colder than it is, a temperature hostile to human life.
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The greenhouse effect
Over thousands of years, changes in atmospheric conditions, such as gas concentrations, and singular events – volcanic eruptions, for instance – have caused climate change. Most of those changes have taken hundreds or thousands of years to play out.
But climatologists now agree that the world appears to be in a sustained, relatively rapid period of warming. The 1990s contained some of the warmest years since records began to be kept in 1861. The year 2004 was the fourth-warmest on record.
Some scientists suggest that global warming will increase the number of extreme weather events such as El Nino and the European heat wave of 2003. Many researchers note the increase in temperature coincides with the industrial revolution, and the resulting increase of carbon dioxide released into the atmosphere from the burning of fossil fuels and the cutting of forests.
» See also: Scientific Differences
According to research cited by the Intergovernmental Panel on Climate Change in 2003, the Earth's average surface temperature has gone up about 0.6 C since the start of the 20th century. That may not sound like much, and many climatologists will agree that it isn't. But some say it's a sign of things to come.
The IPCC projects an average global temperature increase of 0.6-2.5 C in the next 50 years, and 1.4-5.8 C by 2100.
Warming the Earth doesn't necessarily sound like a bad thing, but climate change, especially when it's more rapid than the Earth normally experiences, could have significant effects on animal, plant and human life.
Human activities have increased the level of CO2 in the atmosphere since 1860, as the globe’s average surface temperature rose.
Source: Data from NASA Goddard Institute for Space Studies. (Note: Data prior to 1950 is from ice-core, lake sediment and tree ring samples.)
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Climate change will not happen uniformly. A global temperature increase of 1 C could mean some areas will warm by half a degree, some by three or four, and some may actually get cooler. Scientists tend to point to the Arctic and the Antarctic climates as the signs of things to come. Climate change in those areas is expected to be close to three or four degrees in the winter months. That could lead to glacier melts, rising sea levels, and endangered Arctic wildlife.
The Arctic Climate Impact Assessment from 2004 predicts a reduction in habitat for reindeer, musk ox and caribou. Other studies have suggested polar bears could be threatened. Indigenous people will have their food and cultural systems disrupted. Thinning ice and rising sea levels will also threaten communities.
In an interview with CBC Radio's Quirks and Quarks, University of Victoria Arctic researcher Terry Prowse says, "we often refer to the Arctic as the bellwether, or the canary in the coal mine. Well, that canary is coughing… We've got to keep our eye on it, because 10 years in the Arctic is what we're going to get 30 years down the road."
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