The significance of agnotology
A year or so ago, there was a lot of fuss around the talking point, originating with Richard Lindzen of MIT that “There has been no statistically significant warming since 1995?”At the time, I observed that this meant nothing more than “given the variability in the data, we need at least 15 observations to reject the null hypothesis at 95 per cent confidence”. Thus, it was totally unwarranted to slide, as Lindzen and others did, from “no statistically significant warming” to “no significant warming” or even, in Lindzen’s case “warming has ceased for the past fourteen years”. Sad to say, most of the “sceptics” who profess to “make up their own mind” on the issues, are either too lazy or lack the mental equipment to learn the basic statistics needed to understand this point, and therefore unthinkingly repeated Lindzen’s claim. But, to anyone who understood the issues, it was obvious that a couple more observations in line with the observed warming of recent decades would be enough to bring the trend to statistical significance.
With 2010 over, we now have 16 observations starting in 1995, and (unsurprisingly to anyone who followed the argument thus far) the upward trend is now statistically significant at the 5 per cent level That is, if climate change since 1995 (the time of the first IPCC report, and well after Lindzen announced himself as a sceptic) had been purely random, the odds against such an upward trend would be better than 20 to 1 against.
The obvious question is whether Lindzen will now concede that his claim, and the inference he drew from it, has been falsified, and that warming has not in fact ceased as he suggested. I’m willing to bet that what we see is evasion, obfuscation of or outright silence, not only from Lindzen, but from all of those who parroted his claim.
fn1. My estimates based on the Hadley data used by Lindzen gives an estimated trend of 0.012 degrees a year, with a t-value of 2.45.