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

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Of the three major approaches, the results of the latter technique were said by Shepherd and
Wingham to be “more negative than those provided by mass budget or altimetry.” And why is
that? It is because, as they describe it, the gravity-based technique “is [1 ] new, and [2] a
consensus about the measurement errors has yet to emerge, [3] the correction for postglacial
rebound is uncertain, [4] contamination from ocean and atmosphere mass changes is possible,
and [5] the results depend on the method used to reduce the data.” In addition, they say that
(6) the GRACE record is only three years long, and that (7) it is thus particularly sensitive to
short-term fluctuations in ice sheet behavior that may not be indicative of what is occurring
over a much longer timeframe. Even including these likely ice-wastage-inflating properties and
phenomena, however, the two researchers concluded that the current “best estimate” of the
contribution of polar ice wastage to global sea level change was a rise of 0.35 millimeters per
year, which over a century amounts to only 35 millimeters or a little less than an inch and a
half.
Yet even this unimpressive sea level increase may be too large, for although two of Greenland’s
largest outlet glaciers doubled their rates of mass loss in less than a year back in 2004, causing
many climate alarmists to claim that the Greenland Ice Sheet was responding much more
rapidly to global warming than anyone had ever expected, Howat et al. (2007) reported that
the two glaciers’ rates of mass loss “decreased in 2006 to near the previous rates.” And these
observations, in their words, “suggest that special care must be taken in how mass-balance
estimates are evaluated, particularly when extrapolating into the future, because short-term
spikes could yield erroneous long-term trends.”
Consequently, the most reliable data related to losses of ice from Greenland and Antarctica
suggest that the global sea level rise over the current century should be a whole lot smaller
than the “meters” predicted by the U.S. National Oceanic and Atmospheric Administration’s
James Hansen in testimony presented to the Select Committee of Energy Independence and
Global Warming of the U.S. House of Representatives on 26 April 2007, which in turn implies
that resultant coastal flooding around the world may not even be considered “flooding” -- if it
ever occurs at all! -- based on the best science of our day.
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