The climate fact no one will admit: 2 °C warming is inevitable

[LouisvilleDem]

21. I don't think anyone actually knows

The reality is that we don't know what the 'correct' value for climate sensitivity is.

A committee on anthropogenic global warming convened in 1979 by the National Academy of Sciences estimated climate sensitivity to be 3 °C, plus or minus 1.5 °C, which works out to be 1.5°C - 4.5°C. In the most recent IPCC report (AR5) the IPCC said there is high confidence that ECS is extremely unlikely less than 1°C and medium confidence that the ECS is likely between 1.5°C and 4.5°C and very unlikely greater than 6°C.

So after more than 30 years, we have made absolutely zero progress in narrowing down the range for what is probably the most important value in the science of climate change. I think this is pretty conclusive evidence that anyone who claims to know the actual climate sensitivity value is either lying or seriously deluded.