Global temperature change

Global warming is the warming near the earth's surface that results when the earth's atmosphere traps the sun's heat. The earth is getting warmer. The changes are small, so far, but they are expected to grow and speed up. Within the next fifty to one hundred years, the earth may be hotter than it has been in the past million years. As oceans warm and glaciers melt, land and cities along coasts may be flooded. Heat and drought may cause forests to die and food crops to fail. Global warming will affect weather everywhere, plants and animals everywhere, people everywhere; humans are warming the earth's atmosphere by burning fuels, cutting down forest, and by taking part in other activities that release certain heat trapping gases into the air.

This chart shows the annual increase during the last century.

One major cause of global warming is the use of fossil fuels. Fossil fuels like coal, oil, and natural gas that were formed from the remains of plant material deposited during the earth's carboniferous period. We have known for only a few thousand years that coal, oil, and natural gas can be burned to provide energy. It was not until the mid-1800s, however, that we began to burn very large quantities of these fossil fuels. The worldwide consumption of fossil fuel has increased dramatically.

The world now burns at least five billion tons of fossil fuel each year. As this carbon dioxide from burning fossil fuels enters the atmosphere, some of it is taken up by photosynthesizing plants, and the oceans absorb some. But because we are burning so much fossil fuel at such a rapid rate, we are putting carbon dioxide into the atmosphere much faster than these natural processes are taking it out. There is no longer a balance between the amount of carbon dioxide being added to the air and the amount of carbon dioxide being removed. As a result, the concentration of carbon dioxide in the air is steadily increasing.