Geoscience Reference
In-Depth Information
To put this in perspective, the total volume of ice in the endangered
ice caps is equivalent to approximately 1,600,000,000,000,000,000 gal-
lons of water. This is far beyond what humans can easily pack up to
store in some convenient location. The implications of sea-level rise and
more intense hurricanes are easily comprehended, and in reality human
societies can adapt to them without catastrophic losses. But the implica-
tions of ocean acidifi cation and the potential loss of large numbers of
species are diffi cult to comprehend and value reliably. We cannot rule
out the possibility that future technologies—the analogs of Bill Gates's
patent on hurricane modifi cation—will change the outlook for these
worrisome areas. But the hurdles here are much higher than for man-
aged systems such as health and agriculture—and the prudent course is
to assume these will not be manageable over the next century or so.
Finally, given what is known about impacts, is there a natural limit
for which we can say, “Go up to this point but no further”? It would
simplify policy if we could fi nd some focal point, some precise numeri-
cal target for climate policy. Scientists and policymakers at Copenhagen
in 2009 determined that a temperature increase of 2°C compared to
preindustrial levels was the maximum that was within the safety mar-
gin for earth systems. What does our study of impacts suggest about the
Copenhagen target?
A balanced approach suggests that the 2°C target is both too low
and too high. It is too low given the identifi ed damages analyzed above
and the high costs of attaining such an objective discussed in Part III.
But it is too high a target if we believe, along with many earth scien-
tists, that the earth has already crossed the thresholds of some of the
dangerous tipping points.
How can we resolve this dilemma of whether policies are aiming
too high or too low? The answer lies in the realm of costs. Faced with
the dilemma of deciding between too high and too low, we need to con-
sider the costs of slowing climate change and of attaining different tar-
gets, to which I turn next. When that is completed, we can compare
costs and benefi ts and propose a solution going forward—one that bal-
ances the twin objectives of preserving our environment for the future
while economizing on losses in living standards along the way.
