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The Greenhouse Effect

The atmosphere has a natural supply of "greenhouse gases." They capture heat and keep the surface of the Earth warm enough for us to live on. Without the greenhouse effect, the planet would be an uninhabitable, frozen wasteland.

Before the Industrial Revolution, the amount of carbon dioxide (CO₂) and other greenhouse gases released into the atmosphere was in a rough balance with what could be stored on Earth.

Natural emissions of heat-trapping gases matched what could be absorbed in natural sinks. For example, plants take in CO₂ when they grow in spring and summer, and release it back to the atmosphere when they decay and die in fall and winter.

Too Much Greenhouse Effect

Industry took off in the mid-1700s, and people started emitting large amounts of greenhouse gases. Fossil fuels were burned more and more to run our cars, trucks, factories, planes and power plants, adding to the natural supply of greenhouse gases.

The gases -- which can stay in the atmosphere for at least fifty years and up to centuries -- are building up beyond the Earth's capacity to remove them and, in effect, creating an extra-thick heat blanket around the Earth.

The result is that the globe has heated up by about one degree Fahrenheit over the past century -- and it has heated up more intensely over the past two decades.

If one degree doesn't sound like a lot, consider this: the difference in global average temperatures between modern times and the last ice age -- when much of Canada and the northern U.S. were covered with thick ice sheets -- was only about 9 degrees Fahrenheit.

So in fact one degree is very significant -- especially since the unnatural warming will continue as long as we keep putting extra greenhouse gases in the atmosphere.

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