Some of you may remember how Roy Spencer fudges charts so he can write emotive and alarmist stuff like this (archived here):
I am growing weary of the variety of emotional, misleading, and policy-useless statements like “most warming since the 1950s is human caused” or “97% of climate scientists agree humans are contributing to warming”, neither of which leads to the conclusion we need to substantially increase energy prices and freeze and starve more poor people to death for the greater good.
Roy has just made a belated appearance, commenting on my article where I exposed his shenanigans, writing:
we aligned all of the observations so that the *5 year average* at the beginning of the record (1979-1983) was the starting point. There is NO deception here, nothing nefarious, as you suggest. You can make your own graphs to suggest we did the same as you, but we didn't.
Roy can't have read my article, because what he claims to have done is exactly what I accused him of doing except that I pointed out that what he did was deceitful. In reply I asked him to explain:
Perhaps you will explain why you chose a "five year average" at the beginning of the record and not a thirty year average. Perhaps you will explain why, since you did pick a five year average instead of a thirty year average, you picked that particular five year period when UAH was abnormally high such that it distorted the difference (as I showed above) . Why did you pick 1979-1983
2004rather than, say 2001 to 2005. Why did you move away from your normal baseline of 1981 to 2010?
Roy hasn't explained yet. Anyway, because there were a couple of people who still apparently didn't understand Roy's deception, let's do what I suggested in my comment, and compare using a different five year baseline (2001-2005) and a thirty year 1981-2010 baseline. Here is the result - as always, click to enlarge:
|Data Sources: NASA , UAH , Met Office Hadley Centre and KNMI Climate Explorer|
It should be obvious by now why Roy chose the baseline he did. It was because in that five year period, the UAH readings were abnormally high while CMIP5 mean was on the low side compared with observations. (Compare the 1979-1983 baselined chart with the 1981-2010 baselined chart. As climate watchers know, Roy Spencer reports UAH monthly and annual observations using the 1981-2010 baseline, so his use of the unusual five-year baseline 1979-83 for this exercise is a once-off for his own purposes.)
By picking a very short window where UAH was way above (and other observations were also above) CMIP5, Roy was able to create his illusion. Effectively what Roy's little trick did, was to artificially shift the CMIP5 model runs up compared to observations, making it look as if there is more of a difference than in actuality.
Roy wanted to make the CMIP data look more divergent from observations than they actually are. He used a simple arithmetic trick. Pick an abnormally short window when UAH and CMIP5 are both more divergent from other observations, and in opposite directions, and it will make it appear that there is even more of a divergence. When in fact over the medium term (thirty four years or so) there isn't anything like the difference Roy's trick makes it appear.
What isn't obvious is, when it's pointed out to him, why Roy doesn't just 'fess up to the reason he used his trick.