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The greenhouse effect, as its name implies, describes a warming phenomenon. In a greenhouse structure, closed glass windows cause heat to become trapped inside. The greenhouse effect functions in a similar manner, but on a planetary scale. In general, it occurs when the planet’s atmosphere allows heat from the Sun to enter but refuses to let it leave.

Without this greenhouse effect on Earth, life as we know it would not exist. On our planet, solar radiation passes through the atmosphere and strikes the surface. As it is reflected back toward space, some solar radiation is trapped by atmospheric gases such as carbon dioxide, methane, chlorofluorocarbons, and water vapor, resulting in the gradual increase of Earth’s temperatures. The rest of the radiation escapes back into space. Without this heat, life as we know it would be impossible, Earth would be about 100 degrees cooler, and the oceans would freeze.

Why is global warming important to humans?

The scientific consensus is that global average temperatures are rising, a phenomenon often referred to as global warming. Many scientists believe human activity has greatly contributed to the buildup of greenhouse gases in Earth’s atmosphere in the past century or so, and hence Earth’s gradual warming—around 1 degree Fahrenheit (0.5° Celsius). One recent study by an international panel of scientists predicted that the global average temperature could increase between 2.5 and 10.4° Fahrenheit (1.4 and 5.8° Celsius) by the year 2100 and that sea levels could rise by up to 2 feet (just over a half meter).

What is the biggest culprit? Although there are other gases, such as methane and chlorofluorocarbons, that increase global warming, most experts point to carbon dioxide as the worst pollutant in this case. This gas is released into the atmosphere mainly through burning of fossil fuels, such as coal, gasoline, and diesel. The gas also forms from the destruction of natural vegetation, such as the burning of forests to turn into grazing meadows for livestock. In this case, the carbon dioxide releases in two ways. First, the destruction of plant life through human actions causes less carbon dioxide to be absorbed out of the atmosphere; and secondly, rotting vegetation in clear-cut forests releases carbon dioxide.