Global warming is something that is happening to the climate of the Earth. The average temperature is rising around the world. Why? It’s because of the greenhouse effect.

How does the greenhouse effect increase the temperature?

Have you ever been in a greenhouse? Even on a cold day, it’s warm inside. That’s because the glass lets in heat from the sun but doesn’t let it out again.

The Earth is a bit like a big greenhouse. It is surrounded by a layer of gases—our atmosphere. Some of these gases are called greenhouse gases, because they do what the glass in a greenhouse does. First, they let in the sun’s rays. When the rays get to the ground, some are absorbed as heat. More heat bounces off the land and water and heads back toward outer space. But if it runs into a greenhouse gas on the way, the heat is trapped. It can’t escape into space, so it stays in the atmosphere and warms up the planet.

The greenhouse effect is natural for the Earth, and it’s a very good thing for us. Greenhouse gases are like a blanket that keeps the planet warm. Without the greenhouse effect, the Earth would be much colder than it is now—so cold that the oceans would freeze and we couldn’t live here.

But here’s the thing. Greenhouse gases—especially carbon dioxide—are increasing in the atmosphere because of pollution caused by people. Our "blanket" is getting thicker. The planet is heating up, just like you would if you piled a thick layer of blankets on your bed. You can kick the blankets off if you get too hot. The Earth can’t—and that’s the problem.

Where is the extra CO2 coming from?

From people. We burn coal, oil, and gas (also known as fossil fuels) for energy. Power plants use coal to make electricity. Cars, trucks, planes, and other vehicles run on fuel made from oil. When we burn these fossil fuels, they send carbon dioxide and other greenhouse gases into the air.

Does the hole in the ozone layer have anything to do with global warming?

Is global warming the same as climate change?

What’s the climate? Is it the same as weather?

Weather is what’s happening outside the window right now. It changes from one day to the next—sunny to cloudy, rainy to dry, calm to windy, cool to hot.

Climate is the average weather over time. It’s a pattern we expect to see because it happens in a similar way every year. Different places around the world have different climates. Some places have cold winters and hot summers. Others have a rainy season and a dry season. Some are warm all year round.

The whole Earth has a climate, too. If you average out all the temperatures from the chilly poles to the warm equator, over an entire year, the temperature on Earth tends to be a little less than 60 degrees Fahrenheit (15 degrees Celsius).

A change in the weather is no big deal—it happens all the time. But a change in the Earth’s climate is something that could change our lives in a big way.