Here is an interesting essay/blog post from James Annan, a scientist with the Global Change Projection Research Programme of the Japan Agency for Marine-Earth Science and Technology, and a leading researcher into constraints on estimates of climate sensitivity. Annan has long-held the opinion, borne from his own investigations, that the bounds of the United Nations’ Intergovernmental Panel on Climate Change (IPCC) estimates of the earth’s climate sensitivity are too wide, especially at the high end.
The IPCC’s “fat right-hand tail” of their distribution of possible climate sensitivity values means that the IPCC maintains that there is a non-negligible probability that the earth’s actual climate sensitivity—the global average temperature rise from a doubling of the atmospheric carbon dioxide concentration—is upwards of 6°C (11°F) and perhaps has high a 10°C (18°F). If the climate sensitivity were indeed this high, we’d be in a bunch of trouble. And so long as the IPCC concedes that this possibility exists, it allows folks to gin up truly alarming scare stories for what lies in ahead if we don’t immediately and drastically curtail carbon dioxide emissions.
But Annan has been arguing for years that the IPCC’s stance is scientifically unjustified. And a host of recent scientific studies, including several of his own, seem to have made this point abundantly clear.
But apparently the IPCC is slow to let go of its alarmist notions.
In his recent post, Annan points out that the now-under-construction Fifth Assessment Report from the IPCC (which is due out later this year), continues to hang onto the fat right-hand tail of the distribution, even in the face of a large and growing body of research to the contrary.
But what I find most interesting in Annan’s post is his opinion and insight as to why the IPCC is behaving this way. Annan suggests that the IPCC is more tied to the results of “a small private opinion poll” than it is to the broader literature when it comes to the climate sensitivity estimates.
What follows from Annan is damning:
The paper I refer to as a "small private opinion poll" is of course the Zickfeld et al PNAS paper. The list of pollees in the Zickfeld paper are largely the self-same people responsible for the largely bogus analyses that I've criticised over recent years, and which even if they were valid then, are certainly outdated now. Interestingly, one of them stated quite openly in a meeting I attended a few years ago that he deliberately lied in these sort of elicitation exercises (i.e. exaggerating the probability of high sensitivity) in order to help motivate political action. Of course, there may be others who lie in the other direction, which is why it seems bizarre that the IPCC appeared to rely so heavily on this paper to justify their choice, rather than relying on published quantitative analyses of observational data. Since the IPCC can no longer defend their old analyses in any meaningful manner, it seems they have to resort to an unsupported "this is what we think, because we asked our pals." … [H]aving firmly wedded themselves to their politically convenient long tail of high values, their response to new evidence is little more than sticking their fingers in their ears and singing "la la la I can't hear you". [emphasis added]
The IPCC assessment reports form the science foundation of reports from the U.S. Global Climate Change Research Program, which the Environmental Protection Agency relies on to justify regulating greenhouse gas emissions in the United States.
The significance of all of this should be abundantly clear.