Thread: Happy Earth Day
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Old 05-01-2009, 01:29 PM   #37  
Joined APC: Apr 2009
Position: electron wrangler
Posts: 371
Default Re: Happy Earth Day

Originally Posted by jungle View Post
Here is a target, anyone care to try shooting a few holes in it? Just for sport you understand.

It looks like you left a couple paragraphs out of the middle of this American Geophysical Union/Naval Research Lab joint release.

...After adjusting for other factors, the data from every object indicated a long-term decline in the density of the thermosphere.

This decrease in density had been predicted by theoretical simulations of the upper atmosphere's response to increasing carbon dioxide and other greenhouse gases. In the troposphere (the lowest layer of the atmosphere) greenhouse gases trap infrared radiation, causing the well-known "global warming" effect. Higher in the atmosphere, above about 12 kilometers [seven miles], however, these gases actually enhance the ability of the atmosphere to radiate heat out to space, thereby causing a cooling effect. As the amount of carbon dioxide increases, the upper atmosphere becomes cooler and contracts, bringing lower-density gas to lower heights. Consequently, at a given height, the average density will decrease. Because each layer of the atmosphere rests on the layers below it, small changes at lower altitudes become amplified at higher altitudes. The NRL study found that the observed decrease in density depends on height in the same way as predicted by the theoretical simulations, indicating that greenhouse gases are a likely source of the change.

An extreme example of the greenhouse gas effect can be found on Venus, whose atmosphere is 96 percent carbon dioxide (compared to trace amounts in the Earth's atmosphere), resulting in a very hot lower atmosphere 400 degrees Celsius [800 degrees Fahrenheit] and a very cold and compact upper atmosphere.

These new results verify and significantly expand a limited earlier investigation, by scientists at The George Washington University, which also used orbital data to derive a long-term decrease in thermospheric density...
Increasing greenhouse gases lead to dramatic thinning of the upper atmosphere

Last edited by N2264J; 05-01-2009 at 01:46 PM.
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