What Are Greenhouse Gases? The earth's atmosphere is all around us. As the sunlight enters the earth's atmosphere, it passes through greenhouse gases in the atmosphere. When the sunlight reaches the earth's surface, some of it is absorbed but some is reflected back towards space as infrared radiation (heat). Some of the heat passes back into space, but much of it remains trapped in the atmosphere by the greenhouse gases.

Many chemical compounds found in the earth's atmosphere exhibit these greenhouse properties. Some of them occur naturally (water vapor, carbon dioxide, methane, and nitrous oxide), while others are exclusively human-made (like gases used for aerosols).

Over time, the amount of energy sent from the sun to the earth's surface should be about the same as the amount of energy radiated back into space, leaving the temperature of the earth's surface roughly constant. But scientists today are worried about the "greenhouse effect" caused by gases released by human activities.

What Effect Do Greenhouse Gases Have on the earth? The greenhouse effect is important. Without the greenhouse effect, the earth would not be warm enough for all living species to live. But if the greenhouse effect becomes too strong, it could make the earth warmer than usual (this is called global warming), and rising temperatures may also produce changes in sea levels, and climate. All these may cause problems for humans, plants, and animals. It is still difficult for scientists to determine the extent of change that humans cause. The research done today generally suggests that the earth's climate has warmed over the past century and that human activity is the cause (factories, electricity, and cars release more greenhouse gasses). But we cannot rule out that many changes may also occur naturally.

There are many things we can do to help reduce the greenhouse effect: Save Electricity by turning off lights, the television, and the computer when you are through with them. You can save energy by sometimes taking the bus, riding a bike, or walking. Planting trees is fun and a great way to reduce greenhouse gases. Trees absorb carbon dioxide, a greenhouse gas, from the air. Recycle cans, bottles, plastic bags, and newspapers.