Public Issues
go backCO2 and Global Temperature
by Peter Link
Climate change/energy legislation is prominent in the news. Congress is working on it, and an international panel has met in Copenhagen this past year.
Part of the panel discussion involved the effects of carbon dioxide on climate. Let’s examine CO2 in terms of present and geologic history, and its physical and chemical effects. CO2 makes up 0.037 percent of the atmosphere.
CO2 is more soluble in cold water of polar seas. Higher CO2 content increases acidity of seawater and prevents the growth of coral reefs in polar areas. Less CO2 in warm equatorial latitude seas permits reef growth, generally between 30 degrees N latitude and 30 degrees S latitude.
Global temperatures have warmed since the last ice age, 11,500 years ago. CO2 is released from the oceans following the temperature increase. Vapor pressure of CO2 increases with temperature, forcing CO2 into the atmosphere from the seawater.
In both cases CO2 follows temperature rise and its released.
Absorption spectroscopy determines how much long wave (infrared back to space) radiation CO2 will absorb. Absorbed incoming solar shortwave (UV) radiation heats the Earth’s surface. The radiation absorption spectrum of CO2 absorbs about 8 percent of the outgoing long wave to space, warming the surface. The remaining 92 percent of IR radiation returns to space, cooling the surface. This process can cause freezing at ground level even though ambient air temperatures above ground level exceed 32 degrees.
Residence time of CO2 in the atmosphere indicates that five years is the average time of CO2 in the atmosphere before it is replaced by new CO2. However, CO2 concentrations in the past 600 million years have exceeded present concentrations many times. Some 15.7 million years ago, CO2 levels were the same as today. However, concentrations of up to 7,000 ppm occurred 460 million years ago. Five to 15 times present levels prevailed at other times.
Our planet has been greening since the last ice age with the aid of naturally increasing CO2. Ice cores from Antarctica demonstrate CO2 follows temperature variations.
Modeled attempts to lower the current 385 ppm to 350 ppm would reduce temperature by 0.50 degrees C. Financial costs of such a minimal drop would be very large.
Reliable research says, contrary to much higher model prediction, a doubling of present CO2 would raise global temperatures by 0.5 degrees C, that is, 385 ppm to 770 ppm.
Reprinted with permission from the Canyon Courier newspaper. Published 12/23/2009
Peter Link is a geologist and paleoclimatologist from Evergreen, Colorado.
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