Carbon Dioxide and Earth's Future Pursuing the ... - Magazooms

4. Rising Sea Levels Inundating Coastal Lowlands
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The claim: Anthropogenic-induced global warming will lead to rapidly melting polar ice sheets,
rapidly rising sea levels and catastrophic coastal flooding.
With respect to the melting of earth’s polar ice sheets, we begin in the Northern Hemisphere
with the review of Alley et al. (2005), who claimed that “the Greenland Ice Sheet may melt
entirely from future global warming,” which contention they 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.” Between the periods of
1993-94 and 1998-99, for example, they report that “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,” adding that despite
excess snowfall in the southeast in 2002 and 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.”
Just one day before Alley et al.’s paper appeared in print, however, Johannessen et al. (2005),
working with satellite-altimeter data from Greenland, reported in a Sciencexpress paper posted
online that although below 1500 meters the mean change of the ice sheet height with time was
a decline of 2.0 ± 0.9 cm/year over the 11-year period 1992-2003, above 1500 meters there was
a positive growth rate of fully 6.4 ± 0.2 cm/year due to snow accumulation; and averaged over
the entire ice sheet the mean result was also positive, with a mean growth rate 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, a result that was just the opposite
of that suggested by Alley et al.
Then, like a pendulum changing direction yet again, came the study of Rignot and
Kanagaratnam (2005), who used satellite radar interferometry observations of Greenland to
detect “widespread glacier acceleration.” Calculating that this phenomenon had led to a
doubling of the ice sheet’s mass deficit in the last decade and, therefore, to a comparable
increase in Greenland’s contribution to rising sea levels, they went on to claim that as more
glaciers accelerate, “the contribution of Greenland to sea-level rise will continue to increase.”
Hard on the heels of their paper, however, came the satellite radar altimetry study of Zwally et
al. (2005), which once again sent the pendulum swinging in the opposite direction in response
to their finding that “the Greenland ice sheet is thinning at the margins (-42 ± 2 Gt/year below
the equilibrium-line altitude) and growing inland (+53 ± 2 Gt/year above the equilibrium-line
altitude) with a small overall mass gain (+11 ± 3 Gt/year; -0.03 mm/year sea-level equivalent).”
But Chen et al. (2006) soon after pushed the pendulum way back in the other direction with
their Gravity Recovery and Climate Experiment (GRACE) study, wherein they concluded that
satellite-measured gravity variations suggested that the Greenland Ice Sheet was currently
disappearing at a rate of some 240 cubic kilometers per year. However, the many problems
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