Global Warming

Global Climate Change or Global warming is the unequivocal and continuing rise in the average temperature of Earth's climate system.Since 1971, 90% of the warming has occurred in the oceans.Despite the oceans' dominant role in energy storage, the term "global warming" is also used to refer to increases in average temperature of the air and sea at Earth's surface.Since the early 20th century, the global air and sea surface temperature has increased about 0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980.

Causes of Global Warming

One of the first things scientists learned is that there are several greenhouse gases responsible for warming, and humans emit them in a variety of ways. Most come from the combustion of fossil fuels in cars, factories and electricity production. The gas responsible for the most warming is carbon dioxide, also called CO2. Other contributors include methane released from landfills and agriculture (especially from the digestive systems of grazing animals), nitrous oxide from fertilizers, gases used for refrigeration and industrial processes, and the loss of forests that would otherwise store CO2.
Different greenhouse gases have very different heat-trapping abilities. Some of them can even trap more heat than CO2. A molecule of methane produces more than 20 times the warming of a molecule of CO2. Nitrous oxide is 300 times more powerful than CO2. Other gases, such as chlorofluorocarbons (which have been banned in much of the world because they also degrade the ozone layer), have heat-trapping potential thousands of times greater than CO2. But because their concentrations are much lower than CO2, none of these gases adds as much warmth to the atmosphere as CO2 does.
In order to understand the effects of all the gases together, scientists tend to talk about all greenhouse gases in terms of the equivalent amount of CO2. Since 1990, yearly emissions have gone up by about 6 billion metric tons of "carbon dioxide equivalent" worldwide, more than a 20 percent increase.

Effect of Global Warming

Weather patterns
Hot, dry weather led to a record-setting 2006 wildland fire season with close to 100,000 fires reported and nearly 10 million acres burned, 125 percent above the decade's average.

Health

In July 2006, severe heat waves in North America contributed to the deaths of at least 225 people.
» More on how global warming affects our health.

Wildlife

Scientists report that some polar bears are drowning because they have to swim longer distances to reach ice floes. Unless we take effective action now, the polar bear will likely become extinct in Alaska by 2050.

Glaciers & sea levels

At the current rate of retreat, all of the glaciers in Glacier National Park will be gone by 2070.

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Source:National Geography