Most of Antarctica is Not Warming, New Study Reveals

The view of Antarctic climate just prior to 2009 was that the Antarctic Peninsula was warming rapidly, but that the rest of Antarctica was not. While the warming of the peninsula was deemed to be a "canary in the coal mine"-type of sign of global warming, the lack of warming over the rest of the continent posed a difficult challenge in reconciling observational data with model projections of CO₂-induced global warming. However, the sparseness of weather stations across this huge continent left great uncertainty about these conclusions. In 2009, Steig et al. (S09) provided a method to increase the density of data by utilizing satellite AVHRR data to provide spatial and temporal infilling of data. Their seemingly more complete analysis claimed to show that warming was in fact spread over much of West Antarctica, which is a result that would be much more in harmony with theory and climate models. Their result was featured on the cover of Nature magazine and widely covered in the press as "proof" that warming in Antarctica was worse than thought.

The O'Donnell et al. analysis investigated the Steig et al. paper, and shows that Steig et al. made a number of statistical and analytical mistakes, including (a) improper calibration, (b) spatial structure differences between the infilling operation and recovery of gridded estimates, and (c) suboptimal determination of regularization parameters. The net effect of these errors was to improperly model spatial correlation of the data, which produced a spurious warming in West Antarctica and altered other spatial patterns and trend statistics. O'Donnell et al. also proposed several methods to improve on Steig's analysis. Due to data limitations and because Steig et al. used data from 1957 to 2006, O'Donnell et al. used this same time period. It should be noted that because 1957 was globally cooler than the 1940s, this choice of time period incidentally maximizes any detected trends.

The results are as follows: "Average 1957 - 2006 temperature trends for the continent, East Antarctica and West Antarctica are halved ... maximum warming in West Antarctica occurs in the area adjacent the Peninsula rather than on Ross. East Antarctica displays a persistent cooling feature extending from the South Pole to the Weddell Sea, and large portions of West and East Antarctica display substantially different seasonal behavior. All of these differences are statistically significant at the 5% level."

This new study tends to reinforce the pre-2009 view of Antarctic temperature change: "Our results - including the strong Peninsula warming, insignificant cooling to neutral trend in the Ross region, and generally insignificant trends elsewhere on the continent - compare more favorably to Chapman & Walsh (2007) and Monaghan et al. (2008) than S09." This leaves the main part of Antarctica showing very little trend, which poses a problem for the alarmists since polar regions are supposed to show more response to greenhouse gas warming.

Additional References
Chapman, W. L., and J. E. Walsh. 2007: A synthesis of Antarctic temperatures. Journal of Climate 20: 4096-4117, doi:10.1175/JCLI4236.1.

Monaghan, A.J., D. H. Bromwich, W. Chapman, and J. C. Comiso, 2008: Recent variability and trends of Antarctic near-surface temperature. Journal of Geophysical Research 113: doi:1029/2007JD009094.

Steig, E. J., D. P. Schneider, S. D. Rutherford, M. E. Mann, J. C. Comiso, and D. T. Shindell, 2009: Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year. Nature 457: 459-463, doi:10.1038/nature07669.