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Status of the Greenland Ice-Sheet
Volume 8, Number 44: 2 November 2005

The 21 October 2005 issue of Science contains a major review of recent ice-sheet and sea-level changes (Alley et al., 2005), wherein it is claimed that "the Greenland Ice Sheet may melt entirely from future global warming," which standard climate-alarmist claim is buttressed with the statement that "recently detected rapid ice-marginal changes contributing to sea-level rise may indicate greater ice-sheet sensitivity to warming than previously considered."

The assessment sounds pretty ominous.  But are the data on which it is based really that solid?

Alley et al. say that "for Greenland, updated estimates based on repeat altimetry, and the incorporation of atmospheric and runoff modeling, indicate increased net mass loss."  Between 1993-94 and 1998-99, for example, they say "the ice sheet was losing 54 14 gigatons per year (Gt/year) of ice, equivalent to a sea-level rise of ~0.15 mm/year."  What is more, they report that "despite highly anomalous excess snowfall in the southeast in 2002 to 2003, net mass loss over the 1997-to-2003 interval was higher than the loss between 1993 and 1999, averaging 74 11 Gt/year or ~0.21 mm/year sea-level rise."

Attempting to give these observations even more weight, Alley et al. go on to say they "are broadly similar to those from a mesoscale atmospheric model used to simulate the surface mass balance of the Greenland Ice Sheet from 1991 to 2000," where "accounting for additional mass loss from iceberg discharge and basal melting yielded an estimated net mass loss of 78 Gt/year."

Yes, the data and theory match wonderfully, but the actual observations were very spotty; and a new analysis of a much more comprehensive data set shows the central conclusion of Alley et al. - and that of the atmospheric model - to be 180 degrees out of phase with reality.  And in an incredible irony, the new observations of Johannessen et al. (2005) were reported in a Sciencexpress paper posted online just one day before the Alley et al. paper appeared in print in Science, in an amazing case of the left hand apparently not knowing what the right hand was doing.

In introducing their new observational study, Johannessen et al. note that previous mass balance work on the Greenland Ice Sheet was "based on some tracks of aerial laser altimetry, unevenly sampled in space and time," and that "the surface-elevation data sets analyzed previously have been discontinuous and relatively short."  Overcoming these problems, they derived and analyzed, for practically all of Greenland, a continuous satellite-altimeter height record of ice sheet elevations for the 11-year period 1992-2003.

So what did Johannessen et al. find?  Below 1500 meters, the mean change of ice sheet height with time was a decline of 2.0 0.9 cm/year, qualitatively in harmony with the statements of Alley et al.; but above 1500 meters, there was a positive growth rate of fully 6.4 0.2 cm/year.  Averaged over the entire ice sheet, the mean result was also positive, at a value of 5.4 0.2 cm/year, which when adjusted for an isostatic uplift of about 0.5 cm/year yielded a mean growth rate of approximately 5 cm/year, for a total increase in the mean thickness of the Greenland Ice Sheet of about 55 cm over the 11-year period, which was primarily driven by accumulation of increased snowfall over the ice sheet.  These results turn the central conclusion of Alley et al. (that the Greenland Ice Sheet is shrinking) on its head; and they signal the existence of serious problems with the climate model they cited as agreeing with their faulty view of reality.

In conclusion, it is finally clear that over the past decade or so, at the apex of a global warming that has been characterized as having been the greatest of the past two millennia (Mann and Jones, 2003), the Greenland Ice Sheet has not been wasting away, as climate alarmists claim and as even reputable scientists have been led to believe.  It has been growing, and growing at a very respectable pace.

Sherwood, Keith and Craig Idso

References
Alley, R.B., Clark, P.U., Huybrechts, P. and Joughin, I.  2005.  Ice-sheet and sea-level changes.  Science 310: 456-460.

Johannessen, O.M., Khvorostovsky, K., Miles, M.W. and Bobylev, L.P.  2005.  Recent ice-sheet growth in the interior of Greenland.  Sciencexpress / www.sciencexpress.org / 20 October 2005.

Mann, M.E. and Jones, P.D.  2003.  Global surface temperatures over the past two millennia.  Geophysical Research Letters 30: 10.1029/2003GL017814.