Based on some of the recent comments at the WUWT cross post of my post The Contiguous U.S. Surface Air Temperature Data Through 2012 – Is the Recent Warming Trend Unusual? it became obvious that Tamino was up to his old tricks again. Yup. Tamino is obviously using his normal tactic of misdirection in his post here.
I illustrated in my post the warming periods as they obviously present themselves in the data, and Tamino has presented a 30-year time span of his own choosing for his trend analysis. If we look at the Contiguous U.S. Surface Air Temperatures, Figure 1, the data starts with a cooling period, and that cooling period ended when the surface temperatures reached their minimum at 1917. Looks pretty obvious to me. Surface temperatures then warmed, and they peaked in 1934. Again, it’s obvious. If I had selected other start and end years for that warming period, I would have received numerous complaints. There was then a multidecadal cooling period that started in 1934 and ended when the data reached their second minimum at 1979. After 1979, temperatures warmed.
In an attempt to provide a shorter time period for comparison to the early warming period in my post, I also presented the late warming period with the start year of 1993.
Then there’s Tamino’s post. He used a 30-year time span for his analysis to show that the 30-year trend during the recent warming period had a higher trend than earlier 30-year periods, but he does not illustrate those 30-year periods with the raw data. Here’s why. The period of 1912 to 1941 has the highest 30-year linear trend during the first half of the 20th Century. See Figure 2. It has a lower trend than 30-year periods during the late warming period, because it includes the early warming period AND portions of 2 obvious cooling periods. Would anyone select the years of 1912 to 1941 to define the early warming period? No. They would not. In other words, Tamino selected a time span that does not represent the term of the early warming period.
Tamino comically titled his post “He knows not what he’s doing”. I believe it’s pretty obvious what I’ve done. I’ve selected the warming and cooling time periods as they’ve presented themselves in the data, and I’ve based the trend analyses on those time periods. Tamino calls that cherry-picking. I call it common sense. And it’s also blatantly obvious what Tamino has done. He attempted to draw his readers’ attentions away from the slower rate of warming during the late warming period. It’s called sleight of hand—misdirection.
Has the recent warming period lasted longer than the early period? No doubt about it. Is that any reason to be concerned? No. The mid-to-late 20th Century cooling period lasted for 46 years. Who cares?
What’s obvious is that the warming rate during the recent warming period, though it lasts longer, is much lower than the warming rate of the early period. In other words, there’s nothing alarming about the rate of warming during the recent warming period in the NCDC’s data—even with the cool start year of 1979 and the pleasantly warm 2012 tacked onto the end.
It looks to me like Tamino simply wasted a couple of hours preparing a post for the benefit of his like-minded audience.
Contiguous U.S. land surface air data is available in Table form through the NOAA/NCDC webpage here.