Environment 360, a very useful online magazine, has a new article by Fred Pearce that explains why the next IPCC assessment (AR5) will tell us that the consequences of living with climate change will be even more uncertain than they predicted back in ‘07. Part of this is due to external pressure on IPCC to express uncertainty more honestly than they have in the past, and part is the result of including more feedback processes whose magnitude, and even direction, is not well understood.
Pearce worries about the political fallout from this trend: how will the public respond to the argument that, the more science advances in this field, the less confidence there can be in any particular prediction? I agree, and I think economists are going to have to rethink how they represent the economics of climate change. Point estimates of damages (expected benefits of mitigation) become less relevant to policy as error bars widen; rather quickly, as Weitzman and others have argued, the uncertainty itself becomes the story. Mitigation needs to be seen not as an investment, justified on cost-benefit grounds, but as insurance. What price are we willing to pay to reduce the extreme risks that the next report will include as within the realm of possibility?