This graph shows how the amount of carbon dioxide, a greenhouse gas in the Earth’s atmosphere, has changed over time and how it is expected to change in the future.
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IPCC 2001 Third Assessment Report

The Changing Atmosphere Affects Earth's Climate

The molecules in Earth's atmosphere are always moving and changing as elements such as carbon, nitrogen and oxygen cycle in and out of the air and change through chemical reactions. Even through the individual elements are changing, the proportions of different elements within the atmosphere stays remarkably stable. This stable yet changing state is called dynamic equilibrium. Even though there is equilibrium, there are seasonal changes in Earth’s atmosphere.

Despite the dynamic equilibrium, scientists have found that the amount of greenhouse gases in Earth’s atmosphere has increased over the last 150 years. The rise in amount of greenhouse gases is directly related to human activities such as the burning of fossil fuels, deforestation, and curing of concrete. Humans are affecting the equilibrium and Earth’s cycles such as the carbon cycle, the nitrogen cycle and the water cycle, fundamentally influencing the planet as a whole.

The chemistry of the atmosphere determines what wavelengths of solar radiation are not able to enter the atmosphere, and how much radiation becomes trapped on its way out of the Earth system. Greenhouse gases trap heat through the greenhouse effect. There were greenhouse gases in the atmosphere long before humans affected the system. Having some greenhouse gases in Earth’s atmosphere is beneficial because they keep temperatures mild and suitable for life. However, as the concentration of greenhouse gases has risen, so has Earth’s global temperature. This is causing changes to environments and ecologies worldwide.

Last modified August 13, 2004 by Lisa Gardiner.

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