Hotly disputed UW analysis makes a case for warming

By Sandi Doughton
Seattle Times staff reporter

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But even before the results were published in today's issue of the journal Nature, critics launched into a scholarly version of trash-talking, claiming the University of Washington group is flat wrong.

"It's going to be a very healthy scientific debate," predicted Mike Wallace, a UW climate-change expert who was not involved in the research. "It will take a while to sit down and look at these arguments dispassionately."

Qiang Fu, the lead scientist on the new analysis, said he expected controversy because the topic is central to the debate over climate change and the role of development and air pollution.

"This is a very important question," he said.

Ample evidence shows that temperatures at the planet's surface have risen more than one degree Fahrenheit over the past century, causing glaciers to melt and sea ice to thin.

But until now, studies of the Earth's lower atmosphere — the part where weather occurs — have shown little or no temperature increase.

Global-warming skeptics say that suggests human activity is not changing the climate significantly.

Fu and his colleagues re-examined temperature data collected from weather satellites between 1979 and 2001.

The satellites measure temperature in both the lower and upper atmosphere.

While a human-caused global warming would be expected to raise the temperature in the lower atmosphere, computer models have shown it would have the opposite effect in the upper layer called the stratosphere. And indeed, temperatures there have been dropping steeply over the past several decades.
 
Because satellite measurements from the different layers overlap, Fu suspected the cooling in the stratosphere might be masking any temperature increase in the lower atmosphere.

Fu's team developed a statistical approach to subtract the stratosphere's influence and found the hunch was correct: Temperatures in the lower atmosphere rose about one-third degree per decade, slightly more than the increase seen at the planet's surface during the same time frame.

"I believe this shows the satellite temperatures can no longer be used as evidence to claim that global warming is not happening in the atmosphere," Fu said. "I think this could convince not just scientists but the public as well."

Some fellow scientists were not only unconvinced but dismissive of the study.

John Christy, director of the Earth System Science Center at the University of Alabama at Huntsville, has been analyzing the same satellite data since the early 1990s, finding no evidence of a significant temperature increase. He issued a rebuttal yesterday, saying the UW group went too far in subtracting the stratospheric cooling.

"The method they used creates a false warming signal," said Christy, who believes that humans are changing the climate, but that the changes are modest and not likely to cause ecological disaster.

"Most of the predictions are too alarmist," he said.

Fu deflected the criticism and predicted his team's new study will be the final answer to the long-standing puzzle about atmospheric warming.

"I'm confident this will not be an issue anymore," he said.

As an independent observer, Wallace said he thinks that Fu's approach seems reasonable, but that the debate won't be settled until all the scientists involved have time to hash out the data and the methods.

"I won't profess to claim the verdict is in yet," he said.

Sandi Doughton: 206-464-2491 or sdoughton@seattletimes.com