In Michael Crichtonâ''s silly but immensely successful State of Fear, the plot turns on the ludicrous poetic conceit that climate scientists are not merely sweeping inconvenient facts under the rug, but conspiratorially covering them up. (At the end, the book stops being merely laughable and turns really nasty, with Crichton sadistically killing some of the scientists off.) Among Crichtonâ''s inconvenient truths supposedly being suppressed: the puzzling pause of the earthâ''s warming in the mid-twentieth century, asymmetric climate changes in the northern versus southern hemispheres, andâ''the point Crichton most emphasizesâ''the fact that parts of Antarctica appear to be warming rather than cooling.
In actuality, those issues have been out in the open and under constant discussion among climatologists for decades. I, a mere amateur observer of the ongoing debates, have had a personal theory about the puzzling mid-century pause for years, but as it has no intellectual standing whatsoever, I wonâ''t bore you with it. Nor will I attempt to lay out the various theories about the asymmetric behavior of the poles, as our understanding of the subject appears to be very incomplete, and the technicalities much too complex for anybody but a specialist to truly grasp.
However, Nature Geoscience has published this week, in its Oct. 30 online edition, a major new scientific report on Antarctic warming, along with an exceptionally lucid commentary by Andrew Monaghan of NCAR and David Bromwich of Ohio State. Since the articles appear to be readily accessibly only to people who have Geoscience accounts, I am going to recapitulate the findings in a little more detail than I ordinarily would.
The report, â''Attribution of Polar Warming to Human Influence,â'' is by eight scientists, among whom the principal is Nathan P. Gillett, a climatologist at the University of East Anglia in the UK. In their introductory prÃ©cis, the scientists remind readers that in the most recent report from the Intergovernmental Panel on Climate Change (its fourth assessment), Antarctica is described as the only continent on which anthropogenic global warming has not be conclusively shown. Using novel simulation techniques and data from four major climate models, the climate scientists say they have now found that Antarctic warming must also be human-induced. As the commentary explains, they arrived at this finding by ingeniously disentangling the â''internal and external forcing mechanisms that have contributed to the recently observed variability in near-surface temperature near the poles.â''
By way of background, the commentary notes that Arctic (North Pole) near-surface air temperatures have warmed at about twice the global rate in the last 50 years. â''One of the most dramatic consequences has been the steady decline of sea ice coverage, punctuated by the shocking record minimum in sea ice extent in September 2007â''about 20 percent below the previous recordâ'¿. Other consequences of Arctic warming include increased river runoff, decreased snow cover, permafrost degradation, and a shrinking Greenland ice sheet that is contributing to the rise in sea level.â'' But changes in Antarctica have been much less homogenous. â''Antarctic sea ice over has in general not undergone the marked decline seen for Arctic sea ice, and there has been relatively little change in near-surface air temperatures over the vast East Antarctic ice sheet during the past half century.â''
But in West Antarctica recent ice core evidence shows that the ice sheet underwent â''strong warming with substantial superimposed variabilityâ'' during the past 50-100 years. Several large glaciers in the region are moving faster, adding to sea level rise. On the Antarctic Peninsula, temperature increases of up to 3 degrees Celsius since the 1950s â''are among the largest on Earth for that period.â''
The commentators go on to discuss the relative paucity of observations in Antarctica, and the very considerable uncertainties in accounts of the regionâ''s temperature variations. But this much seems clear: parts of Antarctica have been warming sharply, and those changes are not consistent with natural cycles.
POSTSCRIPT: Michael Crichton's death last week coincided in an unfortunate way with this unabashedly one-sided post. For more scrupulously balanced appraisals of his work, start with Charles McGrath, William Grimes, and Dave Itzkoff in The New York Times.