Heat from the Sun supplies our planet with warmth. But over the past 150 years the amount of heat that is trapped by Earth has increased, causing global warming.
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Courtesy of USGS Astrogeology Research Program

What Controls the Climate?

The Sun
Climate can change if there is a change in the amount of solar energy that gets to Earth. A change in the solar cycle can impact climate. The effect is too small to be the reason that global warming that is happening now. Over thousands of years, changes in the way Earth orbits the Sun can cause big changes in climate too.

When volcanoes erupt they spew more than lava and ash. They also release tiny particles so small that you can’t even see them. These particles get into the stratosphere and reflect solar radiation away from Earth. This shades the planet, causes cooling. After a year or two the little particles fall out of the air and the climate warms up again.

Greenhouse Gases
Greenhouse gases trap heat through a process called the greenhouse effect. Greenhouse gases are a natural part of the atmosphere. But the amount of them has grown over the past 150 years as fossil fuels are burned.

Snow and Ice
Because snow and ice are light in color, they have a high albedo. That means they reflect most of the solar energy that gets to them back out to space. When snow and ice melt as Earth’s climate warms, less energy is reflected and this causes even more warming.

There are also other parts of our planet that have an impact on climate too. For example, scientists are studying the impact of clouds and aerosols on climate.

Last modified June 11, 2008 by Lisa Gardiner.

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