Climate scientists have had to get used to outsiders wandering in from time to time to explain to them how to do their jobs. A famous example was when retired mining consultant Stephen McIntyre clambered into the field of paleoclimatology and busted the hockey stick. A much less famous, but equally impressive example, was when retired financial analyst Nic Lewis strayed into the field of ECS estimation and fixed a few errors. Lewis had a lot of math training, specifically in the impenetrable mysteries of Bayesian statistical modeling which apparently are useful for financial analysis as well as for estimating Equilibrium Climate Sensitivity. In 2013 Lewis published a paper in a top climate science journal in which he reviewed the technique widely used in the field, updated the data and fixed some problems with the math. Voila, not only did the ECS estimate drop but so did its uncertainty range. Previously the data said ECS was somewhere between 2.1 and a whopping 8.9 degrees C with a best estimate of 2.9C. The revised results were, ah, somewhat lower.

Lewis’s new estimate came in between 1.2 and 2.2 degrees C with a best estimate of 1.6C. Not only was ECS lower, but he could rule out that scary upper tail of possible values. You might be wondering why you didn’t hear about it at the time. But as we all know by now journalists aren’t interested in papers that throw cold water on the climate alarm, especially if they have an impenetrably geeky title like “An Objective Bayesian Improved Approach for Applying Optimal Fingerprint Techniques to Estimate Climate Sensitivity.”

On the other hand you might say big deal, what does this guy know? And people in the climatology field were probably tempted to brush him off too. But the problem was that he understood the math better than most of the people working on the problem, so they had to listen. To his credit, Lewis has patiently kept at it, and we will encounter his work several times in this series. Moreover while the climate clique managed to keep his findings out of the most recent IPCC report, they are finding it harder and harder to do so. And if ever they give in and concede that he’s won the argument, IPCC reports will never be the same.