by Willis Eschenbach, November 17, 2018 in WUWT

Let me start explaining the link from Picasso to climate science by looking at what Dr. Nir Shaviv called “the most boring graph I have ever plotted in my life”.

This is the graph of the changes in the best estimate of the range of what is called “climate sensitivity” over the last forty years or so.

What is climate sensitivity when it’s at home? To explain that, I’ll have to take a slight detour. First, downwelling radiation.

“Downwelling” in climate science means headed down towards the planetary surface. Downwelling radiation is the total radiation going downwards towards the surface. It is composed of sunshine (shortwave) plus thermal radiation from the atmosphere (longwave). In climate science, this quantity, total downwelling radiation, is called “forcing”, abbreviated “F”

The central paradigm of modern climate science is that if you change the amount of downwelling radiation (forcing), that the surface temperature perforce will change. The claim is that everything else averages out, and if the forcing increases, then surface temperature needs to change to maintain the global energy balance. It has to change. It must.

In short, the central paradigm of modern climate science is the following:

In the long run, global temperature change is proportional to global forcing change.

The putatively constant proportion between the two, which is the temperature change divided by forcing change, is called the “climate sensitivity”.

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