It might be just worth noting the big nonlinearity
in the system that I do not think is taken account of
in the big IPCC model. That model has gone through
a lot of revisions, some of them a few years ago leading
to a lowering of the forecast of temperature increase.
That one was due to adding in the effect of oceanic
uptake of CO2. Most recently, as most have heard,
the revisions have pushed the forecasts back upward.
The big unmodeled nonlinearity is due to albedo,
reflectiveness. There is a positive feedback effect due
to the expansion or contraction of icecaps and glaciers.
When it cools they expand increasing the reflectivity and
further cooling. The opposite happens during warming,
as now. The upshot is that very large changes in global
temperature can happen in very short periods of time.
Most studies indicate that the temperature changes of
going into or out of ice ages were over very short periods
of time in geological time, e.g. about a century or so.
Barkley Rosser
