Earth's Atmosphere Said
To Have Shrunk 5 Miles
In Last 40 Years
Discovery News Brief
September 16, 1998 -- Scientists from the British Antarctic Survey announced on Tuesday that they have measured a 5-mile (8 km) drop in the Earth's upper atmosphere during the past 40 years. They say that the region is a litmus test for climate change and believe the shrinking is caused by cooling aloft linked to the global warming at the surface. The results, published in this month's issue of the Journal of Geophysical Research, were obtained from radio wave monitoring conducted in studies in Antarctica since 1958.
The altitude decrease they discovered is in the ionosphere, an electric-conducting layer of the upper atmosphere, and was similar to results obtained from separate studies in Europe. This suggests that the change is a global phenomenon. The ionosphere is the hottest and windiest part of the atmosphere where temperatures can vary dramatically during a single day.
Climate change theories have predicted that a doubling of the greenhouse gasses carbon dioxide and methane will raise the earth's surface temperature by about 3.6 degrees Fahrenheit (2 degrees Celsius). But at the ionosphere level, the air could cool by as much as 90 degrees Fahrenheit (50 degrees Celsius). This would cause a much more dramatic shrinking of that upper atmospheric layer.
"The key point here is that it's an indication something's happening to the earth's atmosphere, but it's nothing to worry about," said Dr. Martin Javis of the survey. "It's a sensitive indicator that something's going on and yet another indicator that man seems to be changing his environment."
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