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The Greenhouse Effect
When you step inside a greenhouse, it feels warmer than it does outside. That's because the clear walls let sunlight in, and keep the heated air from escaping.
In a way, Earth acts like a giant greenhouse. Its atmosphere absorbs and holds heat from the Sun, keeping Earth's climate warm enough for life to exist. This heat-absorbing process is called the greenhouse effect. As the Sun's heat energy reaches the atmosphere, some is reflected back into space, while about half reaches Earth's surface. The rest is absorbed by "greenhouse gases" in the atmosphere like carbon dioxide, water vapor, and methane. These gases also absorb heat energy radiating back from Earth's surface.
This is a natural process that keeps the planet livable. But in recent history, human activity is throwing off the balance of greenhouse gasese. By burning fossil fuels, we're releasing carbon dioxide. The more greenhouses gases we put into the air, the more heat they absorb—and the warmer our Earth becomes.
