Ahh, that old chestnut about climate models overestimating the rate of change, which invariably comes with no examples.
The reality is very different.
So much of the modelling has underestimated the rate of change.
To give just one example, the 2007 IPCC Report stated that late summer arctic sea ice is projected to disappear almost completely by the end of the 21st century. It will be lucky to last until mid century at the rate arctic sea ice is disappearing.
In terms of climate models for temperature, they have been pretty damned close, with some underestimating, consider the IPCC modelling:
Note: the IPCC looks at a number of scenarios, the thick black line is the mean scenario with grey lines representing the upper and lower bounds as predicted by their modelling. The coloured lines are actual temperature observations .
1995
Hmm, no overestimating the impact there, more an underestimate.
2001
They're getting closer but still underestimating the rate of change.
2007
The argument that climate modelling is overestimating the warming happening or about to happen is looking weaker by the decade.
2013
Almost spot on, clearly no out of step modelling on the low side.
One other factor - take a good look at the estimates: in the 1995 model they were estimating just on 0.6C of warming by 2020, by the time we get to the 2013 report it is close to 0.9C of warming being predicted by 2020. The models have had to be revised to predict more warming, not less, because the earlier models were out of step . . . the warming is on the high side of the models.
It pays to actually look at the facts.
DS