May 26, 2008	Monday	Jamadi-ul-Awwal 20, 1429

PARIS: Climate change models predicting a dangerous warming of the world’s atmosphere got a confirming boost on Sunday from a study showing parallel trends at altitudes nearly twice as high as Mount Everest.

The new research, published in Nature Geoscience, will help remove one of the remaining scientific uncertainties about the general thrust of global warming, the authors and commentators say.

Over the last two decades, temperature readings from the upper troposphere 12 to 16 kilometres above Earth’s surface based on data gathered by satellites and high-flying weather balloons showed little or no increase.

Oft cited by climate change sceptics, these findings were known to be flawed but still challenged the validity of computer models predicting warming trends at these altitudes, especially over the tropics.

In the new study, climate scientists Robert Allen and Steven Sherwood of Yale University use a more accurate method to show that temperature changes in the upper troposphere since 1970 about 0.65 degrees Centigrade per decade are in fact clearly in sync with most climate change models.

Rather than measuring temperature directly, which had yielded inconsistent results, they used wind variations as a proxy.

“We take an alternative approach by using trends in winds to infer those of temperature,” say the authors. “Winds are observed by radiosonde tracking” which relays data on temperature and humidity from a balloon via radio transmitter “in a matter completely independent from temperature observations”.

There are approximately 10 times fewer discontinuities in wind than in temperature records, making wind measurements a more reliable indicator of long-term trends, notes Peter Thorne of Britain Met Office Hadley Centre in a commentary, also published in Nature Geoscience.—AFP