Published on Thursday, May 6, 2004 by the Guardian/UK
Scientists Claim New Evidence of Warming
by Matthew Taylor
Scientists are claiming to have found compelling new evidence for global warming, finally demolishing the argument of skeptics who have denied the phenomenon is real.
New analysis of satellite data has revealed that temperatures in a critical part of the atmosphere are rising much faster than previously thought, strengthening the worldwide consensus that the earth is warming up.
Until now scientists had been been unable to detect warming in the troposphere, the strata of atmosphere closest to the earth's surface.
This lack of evidence had been seized on by a small but vocal minority of scientists, who have used it to raise doubts about whether global temperatures are rising as a result of human activity.
But now a team led by Qiang Fu, of the University of Washington in Seattle, seems to have solved the puzzle.
His research, reported in the Times, reveals that the troposphere is warming almost precisely as the models predict it should, by about 0.2C per decade. Satellites have not previously detected the trend as they have been confused by colder temperatures in the atmospheric layer above.
The findings, details of which are published today in the journal Nature, provide one of the final pieces of proof that global warming is taking place and that it is a human phenomenon.
Skeptics, including many within the Bush administration, have often argued that if temperatures are rising at all, it is down to natural variation in the climate as the world emerges from a mini-ice age.
The tropospheric trend casts doubt on this theory and is precisely what scientists would expect to see if man-made emissions of greenhouse gases were causing it to heat up.
"I think this could convince not just scientists but the public as well," said Dr Fu.
In the study, the Washington team examined atmospheric temperature data collected between January 1979 and December 2001 from satellites operated by the US National Atmospheric and Oceanic Administration.
The raw data showed no pronounced warming. However, Dr Fu realized that about a fifth of the signal picked up originated in the stratosphere - the higher level of the atmosphere. This had skewed the data, as the stratosphere is known to be cooling rapidly.
"Because of ozone depletion and the increase of greenhouse gases, the stratosphere is cooling about five times faster than the troposphere is warming," said Dr FU.
© Guardian Newspapers Limited 2004