Sep. 22, 1999 The American Geophysical Union's position statement on Climate Change and Greenhouse Gases was published in Eos on February 2, 1999. Like all such statements, it was intended primarily for nontechnical audiences; therefore, it was brief and did not include references to the published scientific literature upon which it was based.
In response to requests for background information and data and as a resource for continuing study of this issue, the authors of the AGU position statement have prepared a thorough, documented analysis of the peer reviewed literature, which will be published in Eos on September 28. Their article, "Climate Change and Greenhouse Gases," was itself rigorously peer reviewed.
Dr. Tamara S. Ledley of TERC in Cambridge, Massachusetts, and her five co-authors have divided the topic into four major areas:
* Greenhouse Gases and the Earth-Atmosphere Energy Balance
* Climate Change and Carbon Dioxide
* Predicted Climate Change from Increased Greenhouse Gases
* Predictive Capabilities and Uncertainties
They conclude that atmospheric concentrations of the principal manmade greenhouse gases (especially carbon dioxide, but also methane, nitrous oxide, and chlorofluorocarbons) have significantly increased during the industrial period. Elevated concentrations are predicted to persist for up to thousands of years. By increasing the amount of infrared radiation absorbed into the atmosphere, these gases produce a warming influence at the Earth's surface.
The authors note that carbon dioxide is not the only influence on global climate change, but that during Earth's long-term geologic history, large-scale variations in carbon dioxide have always been accompanied by simultaneous changes in other components of the carbon cycle and the climate system. In the past 150 years, corresponding to widespread burning of fossil fuels for industrial and transportation purposes that add carbon to the atmosphere beyond that stemming from natural processes, global temperatures have increased on average by 0.5 to 1.0 degrees Fahrenheit (0.3-0.6 degrees Celsius).
The authors predict that further increases in greenhouse gases will cause changes in the climate system. These include increases in average surface temperature, increases in rates of precipitation and evaporation, rising sea level, and changes in the biosphere. The magnitude, geographic distribution, and rate of these changes remain uncertain. These conclusions underlay the AGU position statement on Climate Change and Greenhouse Gases.
The Eos article is accompanied by a list of 189 detailed references to the peer reviewed literature for researchers and others who seek further information. Due to its length, over three pages of small type, the reference list is available only on the AGU web site, not in the printed version of Eos. A limited number of reprints of the article, including references, will be available in mid-October. The reprint will also include the text of the AGU position statement and the procedures under which AGU adopts positions. All of this material is available in one place on the AGU web site: http://www.agu.org/eos_elec/99148e.html, where it may be downloaded and freely copied.
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