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Heating the Atmosphere About 31 percent of the solar radiation is reflected back into space, while the Earth’s atmosphere absorbs 69 percent of it. The surface of the Earth is heated by sunlight that passes through the atmosphere. Upon heating, the Earth’s surface emits infrared rays that warm the air above it. The GHGs present in the Earth’s atmosphere absorb and reemit this infrared radiation. Thus, they act like the glass in a greenhouse, which prevents the heat from escaping.

Human Contribution Human activities, such as excess burning of fossil fuels, release additional GHGs into the atmosphere, thus increasing the green- house effect. CO 2 , methane, and nitrous ox- ide are the main gases that contribute to the GH effect. There are other gases as well that add to the GH effect. However, only a small percentage of them exist in the atmo- sphere.

● ● Among all the GHGs, CO 2 concentrations in the atmosphere. Climate Facts

has the highest

● ● The concentration of CO 2

was less during

the glacial periods. Such periods were marked by colder temperatures.

The Danger of Greenhouse Gases

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