[Updated May8] This post seems to have caused some controversy and even derision in some quarters (especially Lucia’s blackboard). Some of that was even justified. That’s what I get for posting overly quickly (a mistake I won’t make again).
The essential point, though, is that short-term trend analysis is of dubious value when comparing global temperature observations to IPCC projections, because such trends fluctuate so much. Comparisons of the analysis period to the baseline, whether using average anomaly, linear trend or smoothed trend, is likely to be more indicative of the true situation.
Recently, I’ve been commenting to anyone who’ll listen (or not) that short-term comparisons of global temperature trends are not very meaningful and that at least the last 20 years should be analyzed. This was based on the seemingly paradoxical observation that, while trends from 2001 to present are down or flat, long term trends increased during the same period.
Finally someone (Lucia of Blackboard fame) has listened. Unfortunately, she has compared 20-year observed trends to a model subset that has an unrealistically high projected trend.
Click to view animation
A new “analysis” craze has been sweeping the climate contrarian world of late. Not content with cherrypicking one relatively cool La Nina year (even though 2008 was still in the top 10 in the instrumental record), some of the usual suspects are now using higher-order polynomial fitting in an attempt to illustrate a severe downward “trend” in global temperature.
Chief among them (what a surprise) is Alberta’s very own “fact chucker”, National Post columnist Lorne Gunter (you read that right – LG will not rest until all facts are distorted or removed as seen in recent posts here and here). Roy Spencer (of UAH satellite-derived tropospheric temperature fame) has also jumped on the polynomial bandwagon, and now superimposes a polynomial curve on his monthly update of the UAH record. [Update May 15: Spencer no longer uses the fourth-order polynomial curve in his monthly update]. Can a “scientific” conference on the subject, perhaps jointly sponsored by the Heartland and Fraser institutes, be far behind?
Now it turns out that Gunter, who is mathematically challenged to say the least, has most likely been relying on the wisdom and Microsoft Excel skills of his fellow Albertan, oil industry insider and engineer Allan MacRae (or Allan M.R. MacRae, as he most often styles himself). MacRae is a minor but fast rising star in the contrarian firmament, as we shall see.