Go read Ray Pierrehumbert in Slate on the Koonin follies
Let’s imagine you are a smoker and go to the doctor with a variety of troubling physical complaints. She tells you, “Well, a lot of these troubles are typically associated with smoking, but you don’t have cancer yet and the fact is we don’t know everything about the precise biochemical pathways that connect smoking to cancer, and anyway there’s always the chance you’ll get emphysema before you get cancer.” If you were to apply Koonin’s reasoning to this situation, your response would be, “OK, Doc, I’ll wait to give up smoking until you can tell me exactly how it will kill me and when.”
Climate science is settled enough (Bunnies read it here) to provide the policy guidance that matters most, namely that there is an urgent need for halting, and eventually reversing, the worldwide growth in carbon dioxide emissions. At a time when essentially nothing effective is being done, it is pointless to fret, as Koonin does, about exactly how much reduction is optimal—the clear answer from climate science is: “The more the better, the sooner the better, and whatever we actually do is apt to be less than what is really needed, though worth doing nonetheless.” Major policy decisions are routinely made in economic and national security areas in the face of far greater uncertainty than prevails in climate science.and Stefan Rahmstorf at Real Climate explains why the recent jeremiad by David Victor and Charles Kennel advocating giving up on the 2 C limit is hogwash rooted in ignorance (physicist type)
Victor & Kennel claim the 2 °C guardrail was “uncritically adopted”. They appear to be unaware of the fact that it took almost twenty years of intense discussions, both in the scientific and the policy communities, until this limit was agreed upon. As soon as the world’s nations agreed at the 1992 Rio summit to “prevent dangerous anthropogenic interference with the climate system”, the debate started on how to specify the danger level and operationalize this goal. A “tolerable temperature window” up to 2 °C above preindustrial was first proposed as a practical solution in 1995 in a report by the German government’s Advisory Council on Global Change (WBGU). It subsequently became the climate policy guidance of first the German government and then the European Union. It was formally adopted by the EU in 2005.However, Eli believes that, at least as far as the US Government is concerned 3 C is the new 2 C, first the speech by the Director of the Office of Management and Budget, Shaun Donovan, covered at RR
Looking ahead, leading estimates suggest that if we see warming of 3° Celsius above preindustrial levels, instead of 2°, we could see additional economic damages of approximately 0.9 percent of global output per. Our Council of Economic Advisers puts this figure into perspective – 0.9 percent of estimated 2014 U.S. GDP is approximately $150 billion.Last week, Eli went to a symposium at the Brookings institution about the economic effects of climate change moderated by Robert Rubin and featuring Jacob Lew, US Treasury Secretary. Lew too indicated that the administration's planning is based on a 3 C temperature increase. 2 C is a done deal
By its nature budget projections are backwards looking. So as we go through a decade of dramatic weather experiences there is more and more being built into the projections as you see in the size of the disaster relief fund that has grown dramatically over the last decade. I am not sure it encompases every risk out there but it is catching up. GDP, as you know better than I, is a complicated model that is imperfect but does bring in both direct and indirect effects with a very high degree of utility. The projections I referred to that the Council economic advisers did that looks at the impact of three degrees versus two degrees increase in temperature on global GDP reflects the indirect impact of climate through the GDP model.People so high in government don't say such things by accident. Lew summarized
if the debate is about how bad it is going to be, but we know it is going to be bad that is a enough of a case to act. The fact that there is no uncertainty about the direction and legitimate debate about the exactly how bad it is shouldn't be a reason not to actMichael Greenstone, the third member of the panel and a environmental economist at the University of Chicago, actually broke in on Lew to state the real consensus:
There is a line that people have that there is clear consensus among scientists. I think there is one thing that people don't fully appreciate. There is a consensus among the economists about what to do about it. That ranges all the way to Milton Friedman to fill in your favorite left-wing economist who writes for the New York Times. There is a clear consensus about what to do. That is when you are engaged in activity that is harming other people, that activity should be pricey. We should not have a society where it is OK for me to dump garbage in the former secretary's yard.