As described in my last post, I am a “lukewarmer”. That means I acknowledge the scientific principles underlying the theory of AGW. I have little difficulty with the general findings of the IPCC and that anthropogenic sources are responsible for most of the heating observed since 1951. But I also believe that based on the trend of the most recent literature, climate sensitivity will eventually be determined to be at the bottom end of the range reported in the IPCC Working Group I Report. Funny thing though, for the "crime" of expressing this opinion, I have been called a “denier” by the purveyors of the political “consensus” that dominates the on-line discourse in the field.
So I gave in and used the magic word: “consensus”. Up until now I have been talking about the actual scientific consensus. To be clear here, when I talk about the scientific consensus, I am talking about what the IPCC reports and actual climate scientists actually say, not the “consensus” trumpeted in the media by social, political and environmental activists. Why do I distinguish between the two? Well the answer is pretty simple, this thing the activists call the “consensus” has little in common with the actual scientific consensus in the field, as defined by what the IPCC has actually presented in black ink on the pages of its reports. The “consensus” is a political construct created by a band of environmental NGOs and activist organizations. These organizations are made up of well-meaning but essentially scientifically blind [see my previous definition of the term] political activists, social scientists and lay people most of whom are deep in a Dunning-Kruger haze of their own good intentions. Many have read at least some portion of the IPCC Summary for Policymakers. But as those familiar with the process can explain, the Summary document, while initially produced by the scientists, is only approved line-by-line by votes which means that it is a political and not a scientific document. A few of these activists may have read the Working Group I (Physical Science Basis) Summary for Policymakers and virtually none have read (or frankly have the expertise to understand) the actual chapter reports prepared so carefully by the scientific professionals.
Based on the trend of the most recent literature, I expect that the science will settle in the 1.5 oC – 2.5 oC range. So what does that mean? It means that in order to avoid serious consequences in the future we need to identify a path to decarbonizing our power and transport systems. But what else does it mean? Well, if the models predicting low sensitivity (i.e. less than 2 oC per doubling) are correct then the atmosphere can tolerate substantially higher carbon dioxide concentrations than if the sensitivity is higher (say 6oC ). In the lower case maybe mitigation can be used to reduce societal/ecological stress while we work our way towards a goal of stable atmospheric carbon dioxide concentrations (where emissions essentially equal deposition). If it turns out to be 6 oC plus per doubling, then not only had we better ban all coal plants tomorrow, it is unlikely that we can avoid serious ecological damage/cataclysms as we deal with a + 6oC - +10oC world, because even if everything goes perfectly in Lima we are on a path to a doubling plus before we can get this thing in hand.
As I said, were I confident that this alarmist “consensus” was reliable I would argue that immediate responses were necessary and damn the expense. However, I believe that the lower end of the scientific consensus will win out and that means it is time to consider the Precautionary Principal. Wait there is another of those magic terms. I don’t mean the “Precautionary Principal” used by activists to ban all development and scientific advances. I mean the real Precautionary Principal as expressed as Principal 15 in the Rio Declaration which states:
"In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.”