Summary of IPCC AR5 Summary: One man’s best estimate is that same man’s refusal to believe his own data. Emphasis mine:
No best estimate for equilibrium climate sensitivity can now be given because of a lack of agreement on values across assessed lines of evidence and studies. (page 11)
Translation: Our climate models have failed to even approximate the key element for which they were designed.
It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together. The best estimate of the human induced contribution to warming is similar to the observed warming over this period. (page 12)
Translation: In spite of the failure of our models, our best estimate (we’re 95% confident) is that humanity is going to fry if we don’t spend trillions to stop this horrible catastrophe. Stop Keystone, destroy the coal industry, increase “green” subsidies and fund my study, or we all die.