Yale University scientists reported that they may have resolved a controversial glitch in models of global warming: A key part of the atmosphere didn't seem to be warming as expected.
Computer models and basic principles predict atmospheric temperatures should rise slightly faster than, not lag, increases in surface temperatures. Also, the models predict the fastest warming should occur at the Tropics at an altitude between eight and 12 kilometers. However, temperature readings taken from weather balloons and satellites have, according to most analysts, shown little if any warming there compared to the surface.
By measuring changes in winds, rather than relying upon problematic temperature measurements, Robert J. Allen and Steven C. Sherwood of the Department of Geology and Geophysics at Yale estimated the atmospheric temperatures near 10 km in the Tropics rose about 0.65 degrees Celsius per decade since 1970—probably the fastest warming rate anywhere in Earth's atmosphere. The temperature increase is in line with predictions of global warming models.
“I think this puts to rest any lingering doubts that the atmosphere really has been warming up more or less as we expect, due mainly to the greenhouse effect of increasing gases like carbon dioxide,” Sherwood said.
Many scientists, including Allen and Sherwood, have long argued that temperature data were flawed for many reasons such as the change of instrument design over the years. “These systems were never designed for measuring climate change,” said Sherwood. However, some global warming skeptics had argued that weather balloon temperatures were accurate—and models that predicted global warming were wrong.
Allen and Sherwood predicted that measuring thermal winds, which are tied to fluctuations in temperatures, would be a more accurate gauge of true atmospheric warming than the thermometers. To measure the thermal winds, they studied data on the motion of weather balloons at different altitudes in the atmosphere. They then calculated temperatures that would account for the wind velocity recorded.
The findings were reported online May 18 in the journal Nature Geoscience.
- Allen et al. Warming maximum in the tropical upper troposphere deduced from thermal winds. Nature Geoscience, 25 May 2008 DOI: 10.1038/ngeo208
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