re: #32 freetoken

The UKMET is taking into account a possible increase in emissions of CO2 from human sources as well as increasing CO2 from the biosphere as an effect caused by the human input.

Please realize though that there is always a range of possible outcomes… a window if you like, within a given probability range (e.g., a window that would include 95% of the possible outcomes.)

The 4C figure is an upper limit of the “likely” outcomes from the specified scenario.

This gets complicated because there are two large sets of unknowns:
(1) human actions (e.g., how much coal will we burn, how many forests will we chop down…)
(2) the inherent randomness and even more so the essential chaotic nature of the integrated systems on Earth. See the Wiki entry for Edward Norton Lorenz the pioneer in this field.

True. Another disturbing, more political problem arises from this statement:

The study, by Britain’s Met Office Hadley Centre, echoed a U.N. report last week which found that climate changes were outpacing worst-case scenarios forecast in 2007 by the U.N.’s Intergovernmental Panel on Climate Change (IPCC).

So the predictions made by climate models as recently as two years ago were wrong. A situation which seems to occur frequently. Indicating that the models are imperfect, and - given the apparent surprise at the departure from the models reality has taken - that understanding of the underlying mechanisms is also incomplete.

Scientists get themselves into all sorts of trouble when they start making absolute pronouncements instead of doing science. Previous claims made - that the models used are accurate predictors, that the mechanisms of global warming are well enough understood to construct such models with confidence, that doing thus and so will have such and such an effect within so many years - only contribute to distrust of such pronouncements. It would be far less troublesome to simply state the uncertainties, shortcomings and measurable errors associated with such predictions than to make such absolute proclamations and then turn out to have missed the mark, as has happened here.

I’m sure Ludwig will be along shortly to denounce me as a denier, or heretic, without bothering to read what I’ve written. But as I’ve pointed out to him and others before: this sort of misrepresentation of climate modeling is far more of a hindrance than a help in convincing people that anything needs to be done. It make climate scientists look like incompetent chumps.