Earth's Atmosphere


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Greenhouse Effect

Atmospheric greenhouse gases (water vapor, carbon dioxide, methane, and other gases) trap some of the earth's outgoing (infrared) energy, which causes the atmosphere to retain this heat and warm. Life as we know it today would not be possible if it were not for this natural "greenhouse effect". Without the greenhouse effect, temperatures would be much lower than they are today because the energy (heat) would simply escape to space. However, if the atmospheric concentration of greenhouse gases increases, problems may arise.

Since the beginning of the industrial revolution, the atmospheric concentration of certain greenhouse gases has increased. The atmospheric concentration of carbon dioxide, one of the most talked about greenhouse gases, has increased by nearly 30%. Other greenhouse gases have also experienced increases in their concentrations. These increases have enhanced the greenhouse effect (i.e. heat-trapping capability) of the earth's atmosphere.

Scientists generally agree that the increase in the concentration of carbon dioxide is primarily due to the combustion of fossil fuels and other human activities. Another source of carbon dioxide in the atmosphere is from plant respiration and the decomposition of organic matter. Before the industrial revolution all of these carbon dioxide sources were generally in balance with the removal of carbon dioxide through absorption by the oceans and vegetation. As a result, there was no net increase in carbon dioxide concentrations. Human activities (i.e. fossil fuels burned to power car and trucks, heat homes, etc.) have yielded an additional release of carbon dioxide into the atmosphere, increasing its concentration. The rate of climate change, particularly global warming, is likely to accelerate due to the increasing concentrations of greenhouse gases. Since the late 19th century, the global mean surface temperatures have increased 0.5-1.0°F.

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