Background
The authors write that the large mass loss from the Greenland ice sheet over the last decade for which they had data (1995-2005) has caused the impression that "the ice sheet has been behaving anomalously" to the warming of the 1990s and what has followed, which period the world's climate alarmists claim to have been the warmest such interval of the last one to two millennia (Mann et al., 1999; Mann and Jones, 2003). But has the ice sheet's recent mass loss really been than extraordinary?

What was done
In an effort to answer this important question, Wake et al., as they describe it, reconstructed the 1866-2005 surface mass-balance (SMB) history of the Greenland ice sheet on a 5 x 5 km grid "using a runoff-retention model based on the positive degree-day method," which accounts "for the influence of year-on-year surface elevation changes on SMB estimates," while being "forced with new datasets of temperature and precipitation patterns dating back to 1866." This they did, in their words, in order to compare "the response of the ice sheet to a recent period of warming and a similar warm period during the 1920s to examine how exceptional the recent changes are within a longer time context."

What was learned
The six scientists determined, in their words, that present-day SMB changes "are not exceptional within the last 140 years." In fact, they found that the SMB decline over the decade 1995-2005 was no different from that of the decade 1923-1933.

What it means
"Based on the simulations of these two periods," according to Wake et al., "it could as well be stated that the recent changes that have been monitored extensively (Krabill et al., 2004; Luthcke et al., 2006; Thomas et al., 2006) are representative of natural sub-decadal fluctuations in the mass balance of the ice sheet and are not necessarily the result of anthropogenic-related warming."

References
Krabill, W., Hanna, E., Huybrechts, P., Abdalati, W., Cappelen, J., Csatho, B., Frederick, E., Manizade, S., Martin, C., Sonntag, J., Swift, R., Thomas, R. and Yungel, J. 2004. Greenland Ice Sheet: Increased coastal thinning. Geophysical Research Letters 31: 10.1029/2004GL021533.

Luthcke, S.B., Zwally, H.J., Abdalati, W., Rowlands, D.D., Ray, R.D., Nerem, R.S., Lemoine, F.G., McCarthy, J.J. and Chinn, D.S. 2006. Recent Greenland ice mass loss by drainage system from satellite gravity observations. Science 314: 1286-1289.

Mann, M.E., Bradley, R.S. and Hughes, M.K. 1999. Northern Hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations. Geophysical Research Letters 26: 759-762.

Mann, M.E. and Jones, P.D. 2003. Global surface temperature over the past two millennia. Geophysical Research Letters 30: 1820-1823.

Thomas, R., Frederick, E., Krabill, W., Manizade, S. and Martin, C. 2006. Progressive increase in ice loss from Greenland. Geophysical Research Letters 33: 10.1029/GL026075.