Change in Probes May Have Distorted Warming Data

The puzzling difference between warming temperatures on the ground and not-so-warm readings in the sky above may have been resolved.

Atmospheric researchers studying global warming have sought for years to determine why readings taken from weather balloons didn’t show the same increases as readings on the ground. The difference has fueled skeptics of global warming.

Now, researchers at Yale University say exposed instruments on the balloons may have been the problem.

Weather balloons are sent up around the world twice a day -- at local times equivalent to noon and midnight Greenwich mean time.

Older versions of the balloons used temperature probes that were exposed.

The result was higher-than-normal readings on probes sent up in daytime because of the sunlight exposure.

In recent years, however, new probes were developed that were shielded from the light.

Researchers found that although readings rose on the ground they did not increase in the air, since the extra solar heating was no longer warming the probes.

After correcting for the problem, the researchers estimate there has been a global temperature increase of 0.4 degree Fahrenheit, per decade, for the last 30 years.

“Unfortunately, the warming is in an accelerating trend -- the climate has not yet caught up with what we’ve already put into the atmosphere,” said lead author Steven Sherwood, associate professor of geology and geophysics at Yale.

The findings were published Friday in the online issue of the journal Science. The National Oceanic and Atmospheric Administration funded the research.