Complexity and determining dangerous levels of climate impacts

Major advances have occurred in understanding functioning of the atmosphere, oceans, terrestrial ecosystems, cryosphere and all interactions between them. Yet the uncertainty bounds on climate sensitivity, the amount of warming for a doubling of atmospheric carbon dioxide concentrations, remains stubbornly large (IPCC 2013). Although it is totally correct to disclose in full this uncertainty in current knowledge, unfortunately it has the side-effect of forcing a polarization in the debate.