Climate Sensitivity from Paleoclimate Data

Here's a graph from Skinner 2012 that I've never seen before and I'm surprised I've never seen it before--the climate sensitivity from many climate events, warming and cooling, in the distant past:

This is from 

"A Long View on Climate Sensitivity," Luke Skinner

Science 24 Aug 2012, Vol. 337, Issue 6097, pp. 917-919

https://science.sciencemag.org/content/337/6097/917/tab-figures-data

(paywalled). The individual climate sensitivities--the amount of global warming that may be expected as a result of a doubling of the atmospheric carbon dioxide (CO2) concentration--vary, in part because every climate event starts in a different climate and so won't trace the same warming path as any other. Still there's apparently not a lot of variation between events. 

The author gives 12 pairs of data for the different in supplementary material (also paywalled). From it I get a best linear fit to this graph of 

ΔT/ΔF = 0.704°C/(W/m²)

which, using the definition of climate sensitivity λ 

gives, for a doubling of temperature

where α is this proportionality constant equal to 5.35 W/m². Plugging in the numbers

and that quite enough LaTeX for one day. (Like all physics graduate students, I used to be a wiz in LaTeX back then.)

The IPCC 6AR gives a climate sensitivity of 2.5 - 4.0°C, so there is some agreement.