You now know the Earth’s surface and atmosphere stay warm when gases in the air trap heat from the sun. Have you ever been inside a greenhouse, the all-glass buildings where plants are grown? They’re very warm, because the glass walls allow the sun’s rays in but prevent the heat from getting out.
Think of the earth as being inside a giant greenhouse. The gases act like a greenhouse’s glass walls — they keep heat from escaping into space, and the earth stays warm.
Try this easy experiment: Take two jars and put a teaspoon of water in each jar. Put a lid on just one jar. Place both jars in a sunny spot. After a few hours, check on the jars. You’ll see that the open jar hasn’t changed, but the closed jar will be steamy and hot inside. What happened? The heat from the sun could not escape from the closed jar.
The main gases that cause the greenhouse effect are:
Some “greenhouse gases” occur naturally in the Earth’s atmosphere. But scientists measuring the gases say the amount of gases in the atmosphere has increased in the past few decades. For instance, the amount of CO2 in the atmosphere is 30% greater than what it was 150 years ago. Scientists believe CO2 levels will rise another 30% during the next 50 years.
The increase in greenhouse gases is expected to raise the average global temperature of the planet by 2 to 9 degrees Fahrenheit over the next 50 to 100 years.
Most of the increase is due to human activities, like:
All these activities, and many others, release greenhouse gases into the atmosphere. With greater amounts of greenhouse gases in the air, more heat will be trapped, and the Earth will get warmer…and warmer…and warmer.
If Earth gets hotter, some of the following things might occur:
There’s a lot of debate going on about global warming. Some scientists say it’s nature’s way — something that has happened in the past and will likely occur again. Other say global warming is occurring faster because of human beings and that human beings can stop it, or slow it, if they so choose.
One thing is certain: We do not yet know enough about how Earth works to accurately predict what the increase in greenhouse gases caused by humans will do to the planet. The relationships among land, water, air, plants and animals do not follow a simple pattern, where one action automatically leads to the same result.
For instance, an increase in carbon dioxide (the main greenhouse gas) may warm the Earth, and with the greater warmth more trees might grow. Trees absorb carbon dioxide to make wood and grow larger. With more CO2 captured in trees and less CO2 in the atmosphere to hold in heat, the Earth would cool down. Right? On the other hand, trees are also very good at trapping the sun’s heat. So with more trees, the Earth would get warmer. Right?
We really don’t know for sure. After all, the Earth is a big place — a place that’s worthy of your attention and study. Perhaps someday you’ll unlock yet another of Earth’s secrets.
Just because we’re not absolutely certain of how more greenhouse gases will affect the Earth doesn’t mean we should sit back and do nothing.
Besides increasing greenhouse gases, burning too much gasoline and other fossil fuels creates air pollution and wastes energy. Who wants to breathe bad air, or always look up at a dirty sky?
You can help slow global warming by:
Planting trees to help absorb excess CO2, and to provide shade and windbreaks to keep buildings at more even temperatures so they will require less energy for heating or cooling.