Update (March 9th) – Dr. Roy Spencer just gave an interesting response:
“yes, we have been aware of some spurious warming over land versus over the ocean after approximately 2000. Our version 6 dataset (now close to completion) will have most of that removed, although it looks like some of it is genuine.”
I guess we all just have to wait and see …
I have earlier noted a rather curious blocklike shift up in the UAH tlt (lower troposphere temperature) timeseries occurring abruptly some time in 2005. (There is most likely a similar – only downward – step at the same time in the RSS tlt timeseries; however, this post will not address this one.)
The 2005 shift seems very much to originate in the land portion of the UAH dataset. The shift can readily be seen here, but not at all in the oceanic portion, a situation which is quite unprecedented in the record – global land temps simply do not by any known natural mechanism all of a sudden jump out of step with the global ocean temps and then remain elevated high above thereafter:
Figure 1. As you can see, something quite out of the ordinary happens in the UAH land curve in 2005. Continue reading