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BILD 3 - Lecture 24

BILD 3 - Lecture 24 - The amount of CO2 in the atmosphere...

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The amount of CO 2 in the atmosphere is increasing dramatically. The late Charles Keeling and his colleagues at SIO tracked the increase by sampling the clean air at the top of Mauna Loa in Hawaii: The cycles that you see are seasonal fluctuations due to the fact that high levels of photosynthesis in plants living on the land reduces CO 2 levels every northern hemisphere summer. Because there is less land in the southern hemisphere, there is less of an effect on CO 2 levels from this land photosynthesis during the southern hemisphere summer, leading to an increase in CO 2 during the northern winter. In spite of these fluctuations, the overall trend is dramatically upward. CO 2 is a greenhouse gas. It absorbs incident infrared light, which increases the kinetic energy of the CO 2 molecule. Water vapor is the greenhouse gas with the largest effect, and CO 2 is close behind. Oxygen and nitrogen gases, the chief constituents of the atmosphere, do not absorb infrared energy and therefore do not contribute to global warming. It should be noted that greenhouse gases are necessary for life — if there were no greenhouse gases in the atmosphere, the Earth’s average temperature of about 57 degrees F would become close to zero degrees F!
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Methane, another greenhouse gas, is also being released in large amounts through human activity, and each methane molecule is 20 times as effective as CO 2 at trapping heat. Methane is also trapped in large quantities under Arctic ice, and there is some preliminary data suggesting that rapid warming of the Arctic may be starting to release some of these ancient methane deposits. There is 15% more methane in the atmosphere over the Arctic than over other parts of the planet, but we do not have the long-term data to tell us whether this has always been the case, and whether the methane release is increasing. Global warming Is human activity that leads to the generation of CO 2 and other greenhouse gases resulting in global warming? The connection is not proven absolutely, but global temperatures have increased, especially in the last few decades, and glaciers around the world are melting rapidly.
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