Dear Mr. Borenstein, – It would be appropriate to assign a statistical confidence interval as part of a statistical analysis of data, and only then. As you will know, a confidence interval of .95 corresponds to two standard deviations from the mean, and .99 to three standard deviations. However, there was no statistical analysis of the question whether most of the global warming since 1950 was attributable to us: therefore, no statistical confidence interval was appropriate, and the IPCC’s attempt to assign a quantified statistical confidence interval to a non-statistical process was inappropriate and, mathematically speaking, contemptible.
As you will also know, the IPCC was rightly criticized for having assigned a 90% confidence interval (not even a standard interval) to its “consensus” proposition in the Fourth Assessment Report. On that occasion, the political representatives of governments took the decision. Many nations wanted to plump for 95%, for purely political reasons (for there was and is no scientific basis for assigning any quantitative value to such a proposition), but China, for purely scientific reasons, wanted no confidence interval at all. In the end, 90% was settled upon as a compromise, and by no more scientific a process than a show of hands. And these people expect to be taken seriously when they demand the shutdown of the West in the name of Saving The Planet.
By the same token, Mr. Severinghaus’ assertion of a 99% confidence interval to the proposition that CO2 contributes to the greenhouse effect is meaningless. It is demonstrable by simple experiment that adding CO2 or other greenhouse gases to an atmosphere such as ours will cause a radiative forcing that, ceteris paribus, can be expected to cause some warming.
However, temperature feedbacks, non-radiative transports, temperature homeostasis, and chaos in the climate object are among many complicating factors that make it near-impossible to determine with any reliability – even using probability density functions – how much warming will result from a given quantum of forcing, or when it will result, or how long-acting any temperature feedbacks will be. These and many other uncertainties – including the use of a feedback-amplification function at the heart of the climate-sensitivity equation that manifestly has no physical meaning in the real climate – render it impossible to determine whether most of the warming since 1950 was manmade. Accordingly, the IPCC’s pretence that it is 95% confident that most of the warming since 1950 was manmade is transparently rent-seeking guesswork, to which no intelligent journalist should lend the slightest credence.
Frankly, this entire business of the fictitious confidence intervals has become a joke, particularly now that it transpires that just 0.3% of 11,944 papers on global climate change published since 1991 explicitly state support for the IPCC’s version of “consensus”.
In any event, only a Socialist who placed politics before science would believe or assert for an instant that scientific results are determined or reinforced by any form of mere head-counting among scientists. Aristotle demonstrated that argument by mere head-count was a fallacy 2350 years ago. The sheer dumbness of the IPCC’s approach should at least be questioned by journalists, not merely paraded as though it were some sort of Gospel truth. The Holy Books of IPeCaC are no Bible.
There is a huge and fascinating story behind the loutish distortions of scientific, mathematical, physical, and statistical method that have led today’s scientifically-illiterate classe politique to place their faith in propositions – such as the “95% confidence” proposition – that are obvious nonsense. Surely it would be better to start asking real questions than merely to parrot uncritically the innumerate absurdities of a politicized clique of profiteers of doom in the scientific establishment. Time to raise your game. This once-fashionable scare is going down and you don’t want to be dragged down with it. Global warming is no longer cool. It is no longer a happening thing. Indeed, it is no longer happening.
– Monckton of Brenchley