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Cooling the Global Greenhouse?
| Article
# : |
19794 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
3 / 1991 |
2,910 Words |
| Author
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Sherwood B. Idso
Sherwood B. Idso is a research physicist with the USDA's
Agricultural Research Service, an adjunct professor in the
Departments of Botany and Geography at Arizona State
University, president of the Institute for Biospheric
Research, and author of the comprehensive new book Carbon
Dioxide and Global Change; Earth in Transition. |
Millions of years ago the carbon dioxide, or CO2, content of earth's atmosphere was several times greater than it is today. Land and marine plant life thrived in this environment, extracting the abundant CO2 from the air and growing profusely over vast areas of the continents and shallow seas. Over the eons much of the carbon-rich vegetation accumulated in swamps and was ultimately turned into coal. This transfer of carbon from the atmosphere to the lithosphere greatly reduced the air's CO2 content. And as CO2 is the primary raw material used by plants to create carbohydrates via the process of photosynthesis, the reduction in atmospheric CO2 concentration led to a considerable decrease in plant productivity and planetary carrying capacity. With the dawning of the Industrial Revolution, however, man began to mine and burn great quantities of fossil fuels, reversing this process and putting long-sequestered carbon back into the atmosphere at a rate unprecedented in geological history.
Does the rising CO2 level thus portend a revitalization of earth's vegetation and a concomitant increase in the productivity of the biosphere? This question is on the minds of hundreds of plant scientists the world over, as they seek to determine the effects of atmospheric CO2 enrichment on earth's vegetation. The urgency of the quest is highlighted by a number of theoretical climate studies, which suggest that the rising CO2 content of earth's atmosphere may shortly lead to a catastrophic warming of the globe via the so-called greenhouse effect, melting polar ice caps, raising sea levels, flooding coastal lowlands, creating more and stronger hurricanes, disrupting the planet's hydrologic cycle, inducing regional droughts, depressing the agricultural output of many countries, and devastating natural ecosystems. If these predictions are correct, it would clearly make sense to do all in our power to reduce CO2 emissions. But if they are incorrect such measures could needlessly cripple the world economy and deny us the agricultural productivity advantage that may be provided by elevated atmospheric CO2 concentrations, something we may dearly need in the years ahead to feed the ever-increasing mass of humanity.
Adding even more significance to the search for biological consequences of atmospheric CO2 enrichment is the possibility that vegetative productivity may be so greatly enhanced by this phenomenon that plants could withdraw enough CO2 from the air to stabilize the atmosphere's CO2 content at a low-enough level that it would not be climatically disruptive even if the theoretical calculations of earth's climatic sensitivity to CO2 enrichment were correct. Hence, with the nations of the world struggling to determine appropriate
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