January 31, 2009
How does a new Nature study conclude that Antarctica is warming when actual temperature readings show it is not?
For two decades now, those predicting climate-change catastrophe have been frustrated by skeptics who ask, “If carbon dioxide is warming the planet, why does the data show Antarctica to be cooling?” Until last week, the doomsayers had all manner of complicated explanations but no slam dunk answer. Now, thanks to a new study published last week in Nature magazine, the doomsayers obtained the answer they sought — proof that any fool can understand. The bottom line: Antarctica is in fact warming, just like the rest of the planet. “Contrarians have sometime grabbed on to this idea that the entire continent of Antarctica is cooling, so how could we be talking about global warming,” elaborated Michael Mann, director of the Earth System Science Center at Penn State University and a co-author of the Nature study. “Now we can say: No, it’s not true … It is not bucking the trend.”
The press seized on the findings. “Antarctica is warming, not cooling: study,” announced a Reuters headline. “Global warming hits Antarctica,” stated CNN. “Antarctica joins rest of the globe in warming,” said the Associated Press. But this study in Nature leaves many unimpressed, including top scientists from the doomsayer camp. One week after the study’s release, it is clear this study does nothing to explain the enigma of a cooling Antarctica.
The Nature authors had a daunting challenge. For one thing, the U.S. government has maintained a scientific base at the South Pole since 1957 at which temperatures have been continuously measured. The temperature readings show a cooler climate over the past half century. For another, various weather stations in Antarctica record cooler temperatures. Moreover, satellite readings of temperatures above Antarctica show a cooling trend. Little wonder that the UN’s Intergovernmental Panel on Climate Change itself rejects the warming hypothesis. In its 2007 report, the IPCC accepts that Antarctica shows a “lack of warming reflected in atmospheric temperatures averaged across the region.” To reconcile Antarctica with the rest of the globe, global warming advocates have taken the simple, if unsatisfying, view that the lack of warming in Antarctica is consistent with the presence of warming everywhere else.
How do Mann and the other scientists involved in the Nature study now conclude that Antarctica is warming when actual temperature readings show it is not? Antarctica’s weather stations cover a small fraction of the continent. Where data doesn’t exist, Mann makes various assumptions, then deduces Antarctic temperatures over the last 50 years with the help of computer models. The official explanation: “The researchers devised a statistical technique that uses data from satellites and from Antarctic weather stations to make a new estimate of temperature trends.”
Are these statistical techniques reliable?
“I have to say I remain somewhat skeptical,” states Kevin Trenberth, a lead author for the IPCC and director of climate analysis at the National Center for Atmospheric Research. “It is hard to make data where none exist.”
Such results “have no real way to be validated,” states John Christy, an atmospheric scientist at the University of Alabama-Huntsville. “We will never know what the temperature was over the very large missing areas that this technique attempts to fill in.”
“How do the authors reconcile the conclusions in their paper with the cooler than average long-term sea-surface temperature anomalies off of the coast of Antarctica?” asked Roger Pielke, senior scientist at the University of Colorado in Boulder, in noting one of several failings in the study.
Michael Mann and Nature are not new to political controversy, or dubious science. The two collaborated before — in publishing what became known as the hockey-stick graph. This graph — which showed the 1990s to be the hottest decade of the hottest century of the last thousand years — became one of the most publicized facts of the year when it was published. Then the hockey stick became slapstick as it became an object of ridicule: Mann’s statistical techniques were shown to be entirely invalid and Mann was shown to have lacked the statistical knowledge demanded by the study. Mann and Nature refused to make public the data used to produce the graph, Nature refused to publish a response rebutting the hockey stick graph and Nature’s peer review process was shown to be a sham.
It took years, and a U.S. Congressional committee, to finally resolve the dispute, to Mann’s and Nature’s shame. Mercifully, the verdict over the latest offering from these two is seeing a speedier resolution.
Lawrence Solomon is executive director of Energy Probe and author of The Deniers: The world-renowned scientists who stood up against global warming hysteria, political persecution, and fraud.