Background
The authors write that "one of the robust features of the AOGCMs [Atmosphere-Ocean General Circulation Models] is the finding that the temperature increase in the Arctic is larger than the global average, which is attributed in part to the ice/snow-albedo temperature feedback." More specifically, they say "the surface air temperature change in the Arctic is predicted to be about two to three times the global mean," citing the IPCC (2007).

What was done
Utilizing Arctic surface air temperature data from 37 meteorological stations north of 64°N, Chylek et al. explored the latitudinal variability in Arctic temperatures within two belts -- the low Arctic (64°N-70°N) and the high Arctic (70°N-90°N) -- comparing them with mean global air temperatures over three sequential periods: 1910-1940 (warming), 1940-1970 (cooling) and 1970-2008 (warming).

What was learned
In harmony with state-of-the-art AOGCM simulations, the five researchers report that "the Arctic has indeed warmed during the 1970-2008 period by a factor of two to three faster than the global mean." More precisely, the Arctic amplification factor was 2.0 for the low Arctic and 2.9 for the high Arctic. But that is the end of the real world's climate-change agreement with theory. During the 1910-1940 warming, for example, the low Arctic warmed 5.4 times faster than the global mean, while the high Arctic warmed 6.9 times faster. Even more out of line with climate model simulations were the real-world Arctic amplification factors for the 1940-1970 cooling: 9.0 for the low Arctic and 12.5 for the high Arctic.

What it means
These findings constitute another important example of the principle recently described (and proven to be correct) by Reifen and Toumi (2009), i.e., that a model that performs well in one time period will not necessarily perform well in another time period. And this now-incontrovertible fact further suggests that since AOGCMs suffer from this shortcoming, they ought not be considered adequate justification for imposing dramatic cuts in anthropogenic CO2 emissions, as their simulations of future temperature trends may well be far different from what will actually transpire.

References
Intergovernmental Panel on Climate Change (IPCC). 2007. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon et al., Cambridge University Press, Cambridge, UK.

Reifen, C. and Toumi, R. 2009. Climate projections: Past performance no guarantee of future skill? Geophysical Research Letters 36: 10.1029/2009GL038082.