Near-Surface Greenland Air Temperatures: 1840-2007
Box, J.E., Yang, L., Bromwich, D.H. and Bai, L.-S. 2009. Greenland ice sheet surface air temperature variability: 1840-2007. Journal of Climate 22: 4029-4049.
Figure 1. Low-pass-filtered Greenland and Northern Hemispheric near-surface air temperature anomalies with respect to the 1951-1980 base period vs. time. Adapted from Box et al. (2009).
Based on the results depicted in the figure above, the four researchers determined that "the annual whole ice sheet 1919-32 warming trend is 33% greater in magnitude than the 1994-2007 warming," and that "in contrast to the 1920s warming, the 1994-2007 warming has not surpassed the Northern Hemisphere anomaly." Indeed, they note that "an additional 1.0°-1.5°C of annual mean warming would be needed for Greenland to be in phase with the Northern Hemisphere pattern." Thus, there does not appear to be anything unusual, unnatural or unprecedented about the nature of Greenland's 1994-2007 warming episode. In fact, it is much less impressive than the 1919-1932 warming; and it becomes even more "less impressive" when it is realized that the atmosphere's CO2 concentration only rose by about 5 ppm during the earlier period of stronger warming but by fully 25 ppm (five times more) during the later period of weaker warming.