Proof that the recent slowdown is statistically significant (correcting for autocorrelation)

Guest essay by Sheldon Walker

Introduction

In my last article I attempted to present evidence that the recent slowdown was statistically significant (at the 99% confidence level).

Some people raised objections to my results, because my regressions did not account for autocorrelation in the data. In response to these objections, I have repeated my analysis using the AR1 model to account for autocorrelation.

By definition, the warming rate during a slowdown must be less than the warming rate at some other time. But what “other time” should be used. In theory, if the warming rate dropped from high to average, then that would be a slowdown. That is not the definition that I am going to use. My definition of a slowdown is when the warming rate decreases to below the average warming rate. But there is an important second condition. It is only considered to be a slowdown when…