Spread in model climate sensitivity traced to atmospheric convective mixing, Steven C. Sherwood, Sandrine Bony & Jean-Louis Dufresne. Nature. 505, 37–42 doi:10.1038/nature12829.
“This paper offers an explanation for the long-standing uncertainty in predictions of global warming derived from climate models. Uncertainties in predicted climate sensitivity — the magnitude of global warming due to an external influence — range from 1.5° C to 5° C for a doubling of atmospheric CO2. It has been assumed that uncertainties in cloud simulations are at the root of the model disparities, and here Steven Sherwood et al. examine the output of 43 climate models and demonstrate that about half of the total uncertainty in climate sensitivity can be traced to the varying treatment of mixing between the lower and middle troposphere — and mostly in the tropics. When constrained by observations, the authors’ modelling suggests that climate sensitivity is likely to exceed 3° C rather than the currently estimated lower limit of 1.5° C, thereby constraining model projections towards more severe future warming.”
- See also: Climate Change Worse Than We Thought, Likely To Be ‘Catastrophic Rather Than Simply Dangerous and New climate model taking greater account of cloud changes indicates heating will be at higher end of expectations and the Senate testimony of Dr. Roger Pielke of the University of Colorado - “It is misleading and just plain incorrect to claim that disasters associated with hurricanes, tornadoes, floods or droughts have increased on climate timescales either in the United States or globally,” Pielke said. “It is further incorrect to associate the increasing costs of disasters with the emission of greenhouse gases.”