Apparently, Roy Spencer believes that warming indicated by data from the USHCN (U.S. Historical Climate Network) is almost entirely false. He likewise distrusts the trend for the U.S. estimated from the CRUTem3 data. More to the point, he seems to think that warming over the U.S. for the last several decades has been negligible. All but a pittance (a mere 0.013 deg.C/decade), he says, isn’t real, it’s just due to “adjustments.”
Speaking of temperature trend for the U.S., here’s his claim in detail:
The linear warming trend during 1973-2012 is greatest in USHCN (+0.245 C/decade), followed by CRUTem3 (+0.198 C/decade), then my ISH population density adjusted temperatures (PDAT) as a distant third (+0.013 C/decade).
The curious thing is, if you look at the satellite data for lower-troposphere temperature from UAH (Spencer’s own data set), the trend since 1979 for the U.S. is 0.22 deg.C/decade:
The UAH data indicates that the troposphere over the USA is warming 17 times as fast as Spencer’s “PDAT” trend. Even if we allow for uncertainty in the trend from UAH data, we have a 95% confidence interval from 0.088 to 0.356 deg.C/decade. So the tropospheric warming rate might be only 6.8 times as fast as Spencer’s “PDAT” trend. Then again, it might be 27 times as fast.
Does Spencer really believe that the troposphere over the U.S. is warming 17 times as fast as the surface? Or does he not trust his own UAH troposphere data set? It’s a mystery.