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Ocean Biology and Global Climate
| Article
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16968 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
4 / 1990 |
3,475 Words |
| Author
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Paul G. Falkowski and Lisa M. Kirschner
Paul G. Falkowski is the head of the oceanographic sciences
division at Brookhaven National Laboratory in Upton, New
York. Lisa M. Kirschner is in the science and environmental
reporting program at New York University. |
During the last 150 years, more carbon dioxide has accumulated in the atmosphere than at any time in the past 150,000 years.
In the 150,000 years prior to the Industrial Revolution, the earth's atmospheric carbon dioxide concentrations varied from 180 to 290 parts per million of air. During this period, the earth experienced two complete ice age cycles, the most recent of which was at its peak just 18,000 years ago. By 10,000 years ago, the last major glaciers in the Northern Hemisphere had receded.
The advance and recession of major ice sheets covering vast regions of land has been ongoing for more than two million years. These ice age cycles are the result of complex interactions involving air, water, ice, land, lifeforms, radiation from the sun, and long-term variations in the earth's rotation from the sun, and long-term variations in the earth's rotation and orbit. Yet in the last 150 years, human activities have introduced an important new element: The concentration of carbon dioxide in the earth's atmosphere has increased from 275 to 360 parts per million, primarily as a result of the combustion of fossil fuels.
Present-day climate models predict that, as a result of civilization's addition of carbon dioxide to the atmosphere, the world's temperature will rise by 2-15°F. If these models are accurate, man is inadvertently conducting a giant experiment, with himself as the guinea pig.
While the role of and plants in the global balance of carbon dioxide has been widely recognized, the role of microscopic one-celled plants in the ocean, called phytoplankton, has been much less well recognized. In fact, phytoplanktons have played a major role in maintaining the relatively constant level of atmospheric carbon dioxide for millions of years. They continue to influence the climate of the earth today and many help to mitigate some of the effects of industrial activities. Only in recent years has sufficient data accumulated to clarify the subtle dynamics of phytoplankton, carbon dioxide, and other nutrients.
Climate
The average temperature on the surface of the earth is now about 60°F. In a very simplified sense, this temperature is determined by the total amount of infrared light radiated out from the earth's surface that is absorbed by gases in the atmosphere. Next to water vapor, carbon dioxide is the most abundant gas that
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