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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Scientists Clash Over Global Warming--or Cooling?
12 March 1997 6:30 pm
The world should be warming, if climate models predicting the effects of rising levels of greenhouse gases are to be believed. But satellite data seemed to throw cold water on these predictions, suggesting that the atmosphere has in fact become slightly cooler over the last 2 decades. Now two scientists, in a report in tomorrow's issue of Nature, challenge the satellite measurements, suggesting that they actually reveal a slight warming trend. The result, so far, is a heated debate if not a warming world.
Climatologists James Hurrell and Kevin Trenberth of the National Center for Atmospheric Research in Boulder, Colorado, plugged sea-surface temperatures into a model that predicts atmospheric temperatures, then compared the results with actual temperatures measured by microwave-sensing satellites. They found that satellite-recorded temperatures spiked downward twice with respect to the model's predictions--once in 1981 and again in 1991--about the same time that new satellites were put in orbit to collect data. The duo suggests that some of the apparent cooling may arise from a rough transition between satellites. "It's quite spectacular," says Trenberth. Remove those discrepancies, he claims, and "you can completely reconcile the records." The "corrected" satellite data show a weak warming trend of about a tenth of a degree per decade, in line with the climate models.
But the scientists who collect the satellite data are not so easily reconciled. Hurrell and Trenberth are wrong, asserts climatologist John Christy of the University of Alabama, Huntsville. "It's obvious they're not satellite meteorologists," he says. Christy says that in 1981, for instance, two satellites were in orbit collecting data and their data sets "merged perfectly." Meteorologist Alan Basist of the National Climatic Data Center in North Carolina suspects that, rather than indicating flaws in the satellite record, the discrepancy between the two data sets may arise from El Niño warming in the Pacific Ocean and from volcanic eruptions, including Mount Pinatubo in 1991, that occurred at roughly the same time as the spikes.
The debate is unlikely to die soon. Christy and Roy Spencer of the Marshall Space Flight Center in Huntsville have submitted a rebuttal to Nature. Trenberth happens to have been Christy's doctoral adviser. "There's a certain irony there," admits Trenberth. "I wish I had taught him statistics a little better," he adds with a laugh.