The Danger Point: 2 Celsius More Warming?

The Danger Point: 2 Celsius More Warming?

Real Climate
April 7, 2008

“Clearly, the 2°C/450 ppm numbers have completely
permeated the policy-advocacy realm. Yet while
they are arguably derivable from the IPCC
reports, it is actually not clear to what extent
the larger scientific community really believes
these are the right numbers. There simply has not
been a process to evaluate this that compares in
depth and breadth with the IPCC. A new and much
more comprehensive analysis, by a much greater
group of scientists, would be valuable at this
juncture. Scientists are fond of saying that they
cannot summarize their projections with a small
handful of simple numbers, but simple numbers are
what are being discussed in policy circles. If
the “right” numbers are really so low as Jim
Hansen believes (see our post on this, here:

then the Nature Conservancy has an even more
difficult task ahead.”

Real Climate raises important questions about
Hansen’s stance, but concludes with this: “the
conclusion that the Earth System sensitivity is
greater than the Charney sensitivity is probably
robust. And that is a concern for any policy
based on a stabilization scenario significantly
above where we are now.” To see RC’s full review
of Hansen, go here:


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