Geoscience Reference
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In a recent study, Rignot et al. (2011) reported that they had resolved the
disparities between two approaches to estimating ice sheet mass balance in
Greenland and Antarctica over the past eight years. The surface mass balance
(SMB) method utilizes ''the sum of snowfall minus surface ablation reconstructed
from regional atmospheric models with perimeter loss calculated from a time series
of glacier velocity and ice thickness to deduce the rate of mass change,'' whereas
''the gravity method employs a monthly time series of time-variable gravity data
from the Gravity Recovery and Climate Experiment (GRACE) to estimate the
relative mass as a function of time.'' However, their procedures are not only very
complex and detailed, they also appear to require many assumptions of uncertain
veracity. From this, they estimated mass loss rates from the Greenland and
Antarctica ice sheets over the past 18 years based on the SMB method. Over this
period, the annual rate of mass loss has oscillated about a trend that accelerated
at both sites. Annual loss in 2010 was about 250Gt/yr of ice at each site, totaling
about 500Gt/yr for both sites. This corresponds to a rise in sea level of about
1.5mm/yr, which seems a bit high when compared with independent estimates of
sea level rise by direct measurement. Rignot et al. (2011) also noted that the
annual rate of heat loss had accelerated over the 18-year period. They estimated
that acceleration put the sum of both sites at about 36Gt/yr
2
. If this acceleration
persists into the future, it would imply that total sea level rise would be 15 cm by
2050 and 56 cm by 2100. However, there is some alarmist chartsmanship in this
conclusion. There are large oscillations in the data, and the mass gain in 1992-
1993 skews the slope of the acceleration lines. Furthermore, the large positive
loops in Antarctica since 2005 do not seem to be adequately considered. A strong
case can be made for much flatter acceleration lines. In addition, the measure-
ments of sea level suggest that there are long-term oscillations, and extrapolations
of short-term data are not justified.
11.1.4.5 Will global warming prevent or initiate the next ice age?
The First International Conference on Global Warming and the Next Ice Age
14
took
place in August 2001. More than 100 scientists from 13 countries attended. The
conference seems to have rearmed the differences between alarmists and skeptics
on the degrees and causes of climate change, with very few attendees (if any)
changing their positions as a result of the discussions. ''The predictions of the
timing of the next ice age varied between 5,000 and 50,000 years. It was also
suggested that due to the increased levels of carbon dioxide and other greenhouse
gases, the next ice age might never come (a blessing for Canada).''
The Second International Conference on Global Warming and the Next Ice
Age
15
was held in July 2006. Just like the first conference, most of the discussion
focused on human contributions to recent climate change—not on ice ages:
15
journals.ametsoc.org/doi/abs/10.1175/2008BAMS2359.1
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