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It's Snowing on the Climate Alarmists' Party
McConnell, J.R., Arthern, R.J., Mosley-Thompson, E., Davis, C.H., Bales, R.C., Thomas, R., Burkhart, J.F. and Kyne, J.D.  2000.  Changes in Greenland ice sheet elevation attributed primarily to snow accumulation variability.  Nature 406: 877-879.

What was done
The authors derived changes in ice-sheet elevation in southern Greenland for the years 1978-88, using "a physically based model of firn densification and records of annual snow accumulation reconstructed from 12 ice cores at high elevation."

What was learned
Their results agreed closely with those obtained from satellite measurements of ice-sheet elevation change; and, in the authors' words, "we therefore attribute the changes observed in 1978-88 to variability in snow accumulation."  They also determined, from similar analyses of longer ice-core records, that "the decadal-scale changes in ice-sheet elevation that occurred during 1978-88 are typical over the last few centuries and well within the natural variability of accumulation-driven elevation change."

What it means
Quoting the authors, "accurate detection of any long-term mass imbalance of the ice sheets and assessment of likely causes will require multi-decadal time series of surface elevation in conjunction with widely distributed ice-core-derived accumulation measurements collected over the time period of interest."

Put more simply, it will take several decades of several different types of measurements, including snow accumulation, even to be sure that there is a real long-term change - as opposed to natural cyclical variations - occurring in the mass balance of the Greenland Ice Sheet.  And then comes the job of trying to decide what the cause of such a change might be.  So the next time you hear someone getting excited about the Greenland Ice Sheet shrinking (or, to be fair, swelling), tell them to check back in a decade or two; for there's a lot of natural variability to be overcome before we can be sure of anything even remotely related to potential impacts of anthropogenic activities on the pile of ice that is Greenland.

Reviewed 27 September 2000