On the weblog Dot Earth today, there is text from Michael Schlesinger, a climatologist at the University of Illinois, that presents analyses of long term surface temperature trends from NASA, NCDC and Japan as if these are from independent sets of data from the analysis of CRU. Andy Revkin is perpetuating this myth in this write-up by not presenting the real fact that these analyses draw from the same original raw data. While they may use only a subset of this raw data, the overlap has been estimated as about 90-95%.

The unresolved problems with this surface data (which, of course, applies to all four locations) is reported in the peer reviewed paper

Pielke Sr., R.A., C. Davey, D. Niyogi, S. Fall, J. Steinweg-Woods, K. Hubbard, X. Lin, M. Cai, Y.-K. Lim, H. Li, J. Nielsen-Gammon, K. Gallo, R. Hale, R. Mahmood, S. Foster, R.T. McNider, and P. Blanken, 2007: Unresolved issues with the assessment of multi-decadal global land surface temperature trends. J. Geophys. Res., 112, D24S08, doi:10.1029/2006JD008229.

I discuss this issue in my recent post

Further Comment On The Surface Temperature Data Used In The CRU, GISS And NCDC Analyses

where I document that even the CCSP 1.1. report acknowledged this lack of independence.

Andy Revkin’s post on the surface temperature record data sets is not journalistically accurate.