Here is the paper's abstract:
Legal scholarship has come to accept as true the various pronouncements of the Intergovernmental Panel on Climate Change (IPCC) and other scientists who have been active in the movement for greenhouse gas (ghg) emission reductions to combat global warming. The only criticism that legal scholars have had of the story told by this group of activist scientists - what may be called the climate establishment - is that it is too conservative in not paying enough attention to possible catastrophic harm from potentially very high temperature increases.I applaud Johnston for the detail of his cross-examination of the scientific evidence, and for raising important considerations such as the extent to which presumed feedback mechanisms drive both scientific and policy conclusions. But that doesn't mean Marty Weitzman is wrong about the need for "climate insurance" to protect against what he calls the "bad fat tails" of probability density functions (PDFs) of climate sensitivity models. To set policy only according to the means of the PDFs could be a grave mistake.
This paper departs from such faith in the climate establishment by comparing the picture of climate science presented by the Intergovernmental Panel on Climate Change (IPCC) and other global warming scientist advocates with the peer-edited scientific literature on climate change. A review of the peer-edited literature reveals a systematic tendency of the climate establishment to engage in a variety of stylized rhetorical techniques that seem to oversell what is actually known about climate change while concealing fundamental uncertainties and open questions regarding many of the key processes involved in climate change. Fundamental open questions include not only the size but the direction of feedback effects that are responsible for the bulk of the temperature increase predicted to result from atmospheric greenhouse gas increases: while climate models all presume that such feedback effects are on balance strongly positive, more and more peer-edited scientific papers seem to suggest that feedback effects may be small or even negative. The cross-examination conducted in this paper reveals many additional areas where the peer-edited literature seems to conflict with the picture painted by establishment climate science, ranging from the magnitude of 20th century surface temperature increases and their relation to past temperatures; the possibility that inherent variability in the earth’s non-linear climate system, and not increases in CO2, may explain observed late 20th century warming; the ability of climate models to actually explain past temperatures; and, finally, substantial doubt about the methodological validity of models used to make highly publicized predictions of global warming impacts such as species loss.
Insofar as establishment climate science has glossed over and minimized such fundamental questions and uncertainties in climate science, it has created widespread misimpressions that have serious consequences for optimal policy design. Such misimpressions uniformly tend to support the case for rapid and costly decarbonization of the American economy, yet they characterize the work of even the most rigorous legal scholars. A more balanced and nuanced view of the existing state of climate science supports much more gradual and easily reversible policies regarding greenhouse gas emission reduction, and also urges a redirection in public funding of climate science away from the continued subsidization of refinements of computer models and toward increased spending on the development of standardized observational datasets against which existing climate models can be tested.
For all his searching "cross-examination" of the "establishment" climate-science community, Johnston does not seriously challenge the following graph from the IPCC's Fourth Assessment Report (2007), which shows that observed global mean temperature trends confirm models of anthropogenic climate change:
Johnston may be quite right that some climate scientists, such as James Hansen, are basically "doomsayers," who should not dictate policy. But there is no evidence that policy makers are paying much attention to Hansen. And, as Johnston notes, on the issue of sea level rise (which provides the basis upon which Johnston criticizes Hansen), the IPCC's Fourth Assessment Report was, in fact, overly conservative. Johnston expressly recognizes the potential consequences for less developed countries of a two-meter sea-level rise, but may underestimate the consequences for developed countries, including the US.
Finally, from a legal-policy perspective Johnston's presumption that advocacy-based, "establishment" climate models are leading to overly ambitious and expensive climate policies seems to conflate the climate-policy rhetoric of 50-80 percent reductions in GHG emissions by 2050 with the reality of very modest - arguably insignificant - climate policies that have so far been adopted or are presently being contemplated for near-term adoption. His concern about "expensive, immediate and irreversible policy commitments" is, at least so far, unwarranted. Over-commitment to avoiding climate change hardly seems to be the problem right now. Rather, the immediate problem seems to be either no or too little climate policy. Before we concern ourselves with attaining (but not exceeding) some "optimal" level of GHG control, it would be nice if we could at least get the direction right.
UPDATE: I've asked Gavin Schmidt, a climate scientist at NASA, and contributor to the highly respected RealClimate website for his opinion of Professor Johnston's "cross-examination" of climate science. If he e-mails me or posts about it, I will let you know.