- The trend that caught the IPCC by surprise: Since late 2001, the trend of global surface temperatures has been downward. "Global warming" stopped in 1998; and, though it may resume in future years, the rate of warming is self-evidently less than that which the IPCC had expected, and is very likely to be harmless.
- Given the stability of the climate over the past half billion years, there is little danger that current anthropogenic perturbation of the climate will cause a "runaway greenhouse effect". It is likely, therefore, that the IPCC's current estimates of the magnitude of climate feedbacks have been substantially exaggerated.
Here is a summary of his post for those less mathematically literate.
What the two posts show is how much of the official IPCC estimate of climate change is a function of positive feedback within the climate system. Since 1995:
- the proportion of the warming estimate driven by positive feedback estimates has risen from 44% to 68%: the overwhelming majority of the IPCC's basis for predicted warming and dire consequence is an estimation of positive feedback effects within the climate system
- it is not clear that all feedbacks are positive or can all be positive concurrently
- indeed, the overall climate feedback may instead be a negative response within the system: i.e. acting to stabilize and neutralize increased greenhouse gasses, the very opposite of the assumption built into modelling projections and scenarios
- the values used for positive feedback within the latest IPCC report are drawn from a single paper.
But, as William Briggs shows, the fact that the climate models routinely over-predict is positive evidence of something: that some of the suppositions of the models are wrong.
Moreover, as large parts of the world continue to "enjoy" unseasonable weather, it is clear that the world is more endangered by AGW zealotry than any actual climate change.