Earth's atmosphere keeps much of the Sun's energy from escaping into space. This process, called the greenhouse effect, keeps the planet warm enough for life to exist.

Here's a closer look at how it works:


The atmosphere allows about half of the Sun's heat energy (50%) to reach Earth's surface.


About a third of the Sun's energy (30%) is reflected back into space.


The rest of the Sun's energy (20%) is absorbed by greenhouse gases in the atmosphere, like carbon dioxide, water vapor, and methane.


Greenhouse gases in the atmosphere also absorb and hold some of the heat energy radiating back from Earth's surface.


This process has been happening for billions of years. After all, greenhouse gases occur naturally in the atmosphere. But in recent history, human activity is throwing off the balance of greenhouse gases. To get energy or electricity, we burn fossil fuels like coal, oil, and natural gas. This releases carbon dioxide and other greenhouses gases into the atmosphere. The more greenhouses gases we put into the atmosphere, the more heat they absorb—and the warmer our Earth becomes. This is called climate change .