From a citizen perspective, there are three main questions in climate change science: What happened? Who done it? How bad is it going to get? Those questions roughly correspond to the scientific issues of detection, attribution, and climate sensitivity.
All scientists, including skeptics, agree with the IPCC’s assessment that warming of the climate system since the 1950s is “unequivocal.” In contrast, IPCC climate sensitivity estimates are increasingly controversial due to the growing divergence between climate model projections and observed temperatures. The chart below by University of Alabama in Hunstville (UAH) atmospheric scientist Roy Spencer illustrates — and satirizes — the divergence:
Earlier this week, I reviewed a comment letter by Spencer’s colleague John Christy on the scientific basis of EPA’s Clean Power Plan. To recap, EPA’s climate change endangerment analysis is largely based on IPCC climate models. Christy challenges not only the IPCC’s climate sensitivity estimates, but also the IPCC’s claim that most warming since 1951 is anthropogenic. That “attribution” assessment is the core of what IPCC-affiliated scientists and their allies call “the consensus.”
Today’s post offers an historical perspective on Christy’s critique of the consensus position. [click to continue…]