Atmospheric Cooling Figures on Warm Side, Research Finds

Scientists who argue against global warming often cite nearly 20 years of satellite readings showing slight cooling of the atmosphere 2 miles up. But a new study indicates that those readings are incorrect.

The new findings, however, do nothing to settle the debate over whether global warming is really occurring.

Scientists on both sides agree that Frank Wentz, a physicist and chief executive of Remote Sensing Systems in Santa Rosa, Calif., pinpointed the problem with the satellite temperature readings. But that’s as far as they agree.

They continue to debate how the temperatures should be revised and what the revisions mean. No one is changing his or her overall position.

Those who reject the notion that man-made warming of the Earth is occurring say the revised temperatures make an insignificant change. Those who believe that carbon dioxide and industrial gases are heating the atmosphere say the revisions now show a slight warming trend, in line with the warming of the Earth’s surface.

In the study in today’s issue of the journal Nature, Wentz found that the orbit of satellites that take temperature readings decreases over time because of atmospheric drag on the spacecraft. They drop a bit more than half a mile every year, and twice that during some years.

As the satellite slows and drops, the onboard instrument perceives the temperatures below it as cooling, Wentz found.

The perceived temperature change “was just an artifact of the altitude changing,” he concluded.

But when Wentz and co-author Matthias Schabel took the falling satellite effect into account, they found the lower troposphere was warming 0.13 degrees per decade.