Tuesday, April 24, 2007

The Goldilocks Problem

The IPCC uses climate models to make "projections" about climate roughly a hundred years from now. Recall that the IPCC never makes predictions; only projections. I find it strange that the models are considered accurate for this time range yet not other time frames. The models can't predict climate 10,000 or 1,000 years from now because a slight change in initial conditions or model dynamics can lead to vastly different outcomes over time. I wonder if the models have been run for a 1000 years; do they go runaway or get pinned in some final state?

Then there are short time frames, say 1 or 10 years. Down almost into "weather" vs "climate". Again we are told the models don't work at this range. The reasons? Well, there are too many unknowns in this highly dynamic system for the models to be accurate.

Notice I'm not arguing for extreme time frames such as 1 day and 1 million years. At extremes the significant processes in play probably change. But 1 year and 1000 years is reasonable. It would seem that the same reasons (such as Limited Scientific Understanding of climate) preventing the short and long time frame predictions also apply to 100 year predictions. Or is it some sort of climactic sweet spot -- "just right".

A skeptic would say that 100 years is the perfect time frame for scary global outcomes. Far enough way that we won't be around to see if they're correct, but close enough to affect our children or grandchildren.


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