Weather data shows no sign of greenhouse global warming

WASHINGTON — Ten years of weather satellite data show no evidence of global warming from the greenhouse effect, scientists said Thursday, but they added it will take at least another decade of measurements to draw a firm conclusion.

The data, collected from 1979 through 1988 by the TIROS-N series of weather satellites, proved that the Earth’s temperature can be measured accurately by instruments probing the atmosphere from space, two scientists say in a paper to be published Friday in Science.

“We found that the Earth’s atmosphere goes through fairly large year-to-year changes in temperature and over that 10-year period we saw no long term warming or cooling trend,” said Roy W. Spencer, of the Marshall Space Flight Center in Huntsville, Ala.

Spencer’s co-investigator, John R. Christy of the University of Alabama, Huntsville, said that there were temperature swings “that can be quite dramatic” during the decade, but, on a global basis, the thermal changes tended to even out.

“The northern hemisphere goes up slightly during those 10 years and the southern hemisphere goes down slightly,” said Christy. “The net effect for the globe is basically zero.”

Detecting a climate trend, the scientists said, will take at least another decade of satellite measurements.

“There is no guarantee that if you take a 10-year segment out of a long time that you’ll get the overall trend,” said Christy. “The data cannot be used to say we’ve got an enhanced greenhouse effect.”

Christy said the findings “are enough to tantalize us … but this is just a start” and satellite measurements are continuing.

“By the turn of the century, we should see a trend,” said the scientist.

The TIROS satellite data is the first to add global temperature data to the scientific debate about the greenhouse effect, Spencer said. Most other studies of temperature trends, some extending over more than a century, have come from the records of ground-based thermometers. These readings, he said, do not reflect the global temperature because there are very few temperature measurements for vast areas of the Earth’s oceans.

Some experts believe that the Earth is beginning to warm up as a result of carbon dioxide and other gases dumped into the atmosphere over the last 150 years of industrial civilization. This warming, called the enhanced greenhouse effect, is a matter of controversy in the scientific community because of the difficulty in measuring small climate trends over a long period of time.