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The Forecast: A Warmer World

Right now, ancient glaciers are slowly melting and shrinking like ice cubes in a glass of soda. Beaches that were once wide stretches of sand are becoming narrow strips as the ocean level rises. The earth's climate is changing. The whole planet is warming up.

Changes in climate are part of nature. Over the ages, there have been cold periods and warm periods. But the changes predicted for the next century are dramatic, and some scientists say this time humans are partly to blame.

According to a new report by a United Nations scientific group, the earth's average temperature could rise as much as 6ºF in the next 100 years! That would be a huge change. Over the past 100 years, the average temperature rose 1ºF, and even that is considered to be a big change.

These scientists say there is new evidence that pollution from factories, cars and other human sources is causing this "global warming." They used the latest computer models to make their predictions. If pollution like this continues, the report warns, our planet will be a warmer place by the 2030s than it has been for 2 million years. This will have an enormous effect on the earth's inhabitants.

Some climate experts question this view. They say that global warming is part of a natural pattern and that human habits are not really at fault. Still, almost everyone agrees that earthlings should get ready for changes in the climate.

The Greenhouse Trap
The earth stays warm the same way a greenhouse does. Gases in the atmosphere act like the glass of a greenhouse: they let in the sun's light and warmth, but they keep the earth's heat from escaping back into space. Without this "greenhouse effect," the earth would be too cold for most plants and animals.

But if there is too much gas trapping heat, things get out of balance. Not enough heat can escape. Temperatures rise around the world. That's global warming.

The Human Factor
Many kinds of pollution send heat-trapping gases into the atmosphere. The most plentiful "greenhouse gas" is carbon dioxide (CO₂), created by burning wood, and other fuels. Trees can absorb CO₂ and turn it into pure oxygen. People make global warming worse by cutting down forests full of trees that would have soaked up extra CO₂.

Other greenhouse gases clog the atmosphere too. Chlorofluorocarbons are greenhouse gases that people use to cool the air in air conditioners and refrigerators. Methane gas rises from rotting garbage and animal waste. Nitrogen oxides come from car exhaust and power-plant smokestacks.

High Water, Cruel Weather
Even a small rise in the earth's temperature could have a big impact. The U.N. scientists predict that over the next century, polar ice and glaciers could melt, raising ocean levels as much as three feet. Low-lying land along seacoasts and in river basins could flood. Entire islands in the Pacific could be under water. Many people could have to move to higher ground. Other species could suffer.

Global warming could also make weather less predictable, with extreme heat and cold, drought and more violent storms. Rainfall patterns could change. Some farm areas could be unable to grow crops. Places too cold now could be good for farming.

What can we do? Most nations have taken small steps to control the release of gases that trap heat. Nearly everyone agrees that stronger measures are needed, but it is hard for people to change old habits. Scientists now know global warming can't be ignored much longer.

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The Greenhouse Effect

1. Sunlight hits the earth, giving it warmth and energy.
2. Carbon dioxide (CO₂) in the atmosphere traps some of the heat, keeping the earth warm.
3. As pollution increase, CO₂ and other heat-trapping gases build up. The earth grows hotter.

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