AR5 (as Nic Lewis regularly points out) concludes a most likely net aerosol offset of -0.9 watt / M ^ 2, which is bizarrely inconsistent with the average level of aerosol offsets used by the AR5 climate model ensemble (much higher offsets in the models), and most consistent with a fairly low (< 2C per doubling) climate sensitivity to forcing. (judithcurry.com)