Dear EarthTalk: What exactly is the “greenhouse effect” and how is it a bad thing?

Dear EarthTalk: What exactly is the “greenhouse effect” and how is it a bad thing?

—Suanne Gladstone, Queensland, Australia

The “greenhouse effect” occurs naturally when heat from the sun enters our atmosphere but cannot escape because it is blocked by water vapor, carbon dioxide and other airborne elements, thereby causing a warming of the Earth. Without a natural greenhouse effect, the average temperature of the Earth would be about zero degrees Fahrenheit instead of its present 57 degrees Fahrenheit.

But increasing amounts of pollutants from manufacturing and power plants, agricultural activities, automobiles and other sources that burn fossil fuels have led to an excessive build-up in the Earth’s atmosphere of “greenhouse gases” such as carbon dioxide, nitrous oxides and methane. Scientists believe that this build-up is exaggerating the naturally occurring greenhouse effect and is to blame for the average temperature on Earth rising by more than one degree over the last century.The International Panel on Climate Change, an international group of climatologists, predicts that Earth’s temperature will continue to rise from two to 10 degrees Fahrenheit during this century as a result of human industrial activity. According to the Sierra Club, the likely effects of this global warming include the melting of massive icebergs and glaciers, sea level rise, accelerated coastal erosion, more (and more severe) hurricanes, the spread of infectious diseases and widespread species extinctions, among other problems.

To address this crisis, 127 countries have agreed on mandatory curbs on greenhouse gas emissions via an international treaty set to go into effect in 2005 called the “Kyoto Protocol.” The treaty is so-named because it was the outcome of a meeting held in Kyoto, Japan in 1997. Under the Protocol, the United States is supposed to cut its greenhouse gas emissions by seven percent by the period between 2008 and 2012. With four percent of the world’s population, the U.S. currently accounts for about 25 percent of the Earth’s greenhouse gas emissions. The U.S., however, has refused to sign this United Nations-backed agreement, arguing that U.S.compliance with the terms of the treaty would harm the American economy.

But, according to the Natural Resources Defense Council (NRDC), some of the U.S. government’s own studies should quell such fears: “While industry trade associations have published many misleading claims of economic harm,” says NRDC, “two comprehensive government analyses have shown that it is possible to reduce greenhouse pollution to levels called for in the Kyoto agreement without harming the U.S. economy.”Instead, the U.S. is pushing for technological approaches that would remove carbon dioxide from the atmosphere and store it below ground or under water. But environmentalists fear that loading massive mounts of carbon dioxide into the Earth and oceans could wreak ecological havoc in other ways, and doubt that human-induced global warming can be solved by American ingenuity alone.

CONTACT: Kyoto Protocol, ; International Panel on Climate Change, ; Sierra Club Global Warming and Energy Program, (415) 977-5500, ; Natural Resources Defense Council, (212) 727-2700, .