By Juliet Eilperin
Washington Post Staff Writer
Wednesday, May 3, 2006; A03
A government study released yesterday undermines one of the key arguments of climate change skeptics, concluding there is no statistically significant conflict between measures of global warming on the earth's surface and in the atmosphere.
For years some global warming critics had pointed to the fact that satellite measurements had recorded very little warming in the lower atmosphere, while surface temperature readings indicated that the earth is heating up. Now the U.S. Climate Change Science Program, an interagency body, has concluded the two data sets match.
"The bottom line is there are no significant discrepancies in the rates of warming," said Thomas R. Karl, director of the National Climatic Data Center at the National Oceanic and Atmospheric Administration, in a telephone call with reporters. Karl said reconciling the two sets of temperature readings is "really a major step forward" in understanding climate change.
The report also concluded that humans are driving the warming trend through greenhouse gas emissions, noting in the official news release, "the observed patterns of change over the past 50 years cannot be explained by natural processes alone, nor by the effects of short-lived atmospheric constituents such as aerosols and tropospheric ozone alone."
Rafe Pomerance, chairman of the Climate Policy Center, a group that advocates mandatory curbs on emissions of carbon dioxide and other greenhouse gases linked to global warming, said the new report settles the scientific debate over humans' role.
"This puts the nail in the coffin of [the skeptics'] argument as much as anything I've seen," Pomerance said. "It may not be the first time it's been said, but it's the clearest I've seen it stated coming out of a government agency. Game over."
Twenty-one scientists worked on the federal report, Karl said, and concluded that more recent satellite data -- coupled with some corrections to earlier analyses -- had reconciled surface temperature observations with satellite records.
Still, the new findings did not sway several scientists and politicians who question whether the climate is changing dramatically.
Senate Environment and Public Works Committee Chairman James M. Inhofe (R-Okla.), who maintains there is no evidence that human activity is warming Earth, noted that observed land temperatures have risen about the same amount over the past 30 years as in the period from 1918 to 1945, when industrial sources were emitting fewer greenhouse gases.
"What is clear is that our increased confidence in land-based temperature data in no way implies or supports a conclusion that recent observed warming is due to man instead of natural variability," said Inhofe's spokesman, Matthew Dempsey.
Inhofe's analysis does not account for the acceleration in global surface temperatures since the mid-1970s on top of earlier warming at the turn of the century, Pomerance said, and Earth has now entered the warmest period on record.
John Christy, who directs the Earth System Science Center at the University of Alabama at Huntsville, thinks humans are contributing to global warming but had long pointed to the discrepancies between surface and atmospheric readings in challenging predictions of future rapid climate change. A co-author of yesterday's federal study, he said he has "a minimalist interpretation" of the report because Earth is not heating up rapidly at this point.
"That doesn't change my whole view of the thing, because the whole rate of change is fairly modest," Christy said in an interview.
He added that in the tropics, climate models predict higher temperatures in the atmosphere than at the surface, something scientists are still investigating.
In a separate study published Monday in the journal Climate, NOAA scientists determined that human activity has helped warm the area of the tropical Atlantic where many hurricanes originate. The paper, by scientists at the Geophysical Fluid Dynamics Laboratory in Princeton, N.J., concluded that human-induced warming "in various tropical ocean basins" could affect the intensity of hurricanes stemming from the region.