Geoscience Reference
In-Depth Information
ice sheets. The fi rst is the Greenland Ice Sheet, which has about 7 me-
ters (23 feet) of SLR equivalent of ice. This means that if the Greenland
Ice Sheet were to melt completely, sea level would rise about 7 meters.
A second concern is the West Antarctic Ice Sheet, which has an SLR
equivalent of about 5 meters (16 feet). The balance of the Antarctic ice
sheet has a much larger volume of ice, but the ice there is so cold and
fi rmly grounded that there seems little risk of melting for several cen-
turies.
Chapter 5 discussed the processes and possible tipping points asso-
ciated with the melting of the Greenland Ice Sheet. Modeling ice caps is
extremely diffi cult, according to specialists in this area. Recent estimates
are that melting glaciers and ice caps will contribute 0.2 meters (8 inches)
of SLR by 2100. Other projections using statistical techniques have pro-
duced larger estimates, but these have not been validated by ice sheet
much to SLR as thermal expansion. It must be emphasized, however,
that this is an active area of scientifi c research, and we must be pre-
pared for “inevitable surprises” in the future.
6
As I have emphasized above, a major goal of climate research is to
integrate economic and environment projections. This applies to SLR as
well. The standard scenarios for SLR are decoupled from the economy,
and vice versa.
How do integrated economy-SLR models behave? To illustrate this
question, I have used the DICE model to make projections of climate-
change impacts for different scenarios over the coming centuries. The
model includes all sources of SLR, although the dynamics of the ice
caps are very uncertain. The projections are consistent with standard
ocean-climate models but additionally are linked to the economic and
emissions models.
7
For this exercise, we can look at two different emissions trajecto-
ries. One scenario uses baseline (unconstrained) emissions. I discussed
the baseline concept in earlier chapters. The second model run assumes
that global temperature increase is limited to a 2°C increase over the
1900 level. This target was endorsed in the Copenhagen Accord and is
further analyzed in later chapters.
