An article has appeared in Nature on May 13 2010 titled
Peter A. Stott and Peter W. Thorne, 2010: How best to log local temperatures? Nature. doi:10.1038/465158a, page 158 [thanks to Joe Daleo for alterting us to this]
which perpetuates the myth that the surface temperature data sets are independent from each other.
The authors know better but have decided to mislead the Editors and readers of Nature.
“In the late twentieth century scientists were faced with a very basic question: is global climate changing? They stepped up to that challenge by establishing three independent data sets of monthly global average temperatures. Those data sets, despite using different source data and methods of analysis, all agree that the world has warmed by about 0.75 °C since the start of the twentieth century (specifically, the three estimates are 0.80, 0.74 and 0.78 °C from 1901–2009).”
This is deliberately erroneous as one of the authors of this article (Peter Thorne) is an author of a CCSP report with a different conclusion. With just limited exceptions, the surface temperature data sets do not use different sources of data and are, therefore, not independent.
As I wrote in one of my posts
In the report “Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences Final Report, Synthesis and Assessment Product 1.1” [a report in which Peter Thorne is one of the authors] on page 32 it is written [text from the CCSP report is in italics]
“The global surface air temperature data sets used in this report are to a large extent based on data readily exchanged internationally, e.g., through CLIMAT reports and the WMO publication Monthly Climatic Data for the World. Commercial and other considerations prevent a fuller exchange, though the United States may be better represented than many other areas. In this report, we present three global surface climate records, created from available data by NASA Goddard Institute for Space Studies [GISS], NOAA National Climatic Data Center [NCDC], and the cooperative project of the U.K. Hadley Centre and the Climate Research Unit [CRU]of the University of East Anglia (HadCRUT2v).”
These three analyses are led by Tom Karl (NCDC), Jim Hansen (GISS) and Phil Jones (CRU).
The differences between the three global surface temperatures that occur are a result of the analysis methodology as used by each of the three groups. They are not “completely independent”. This is further explained on page 48 of the CCSP report where it is written with respect to the surface temperature data (as well as the other temperature data sets) that
“The data sets are distinguished from one another by differences in the details of their construction.”
On page 50 it is written
“Currently, there are three main groups creating global analyses of surface temperature (see Table 3.1), differing in the choice of available data that are utilized as well as the manner in which these data are synthesized.”
“Since the three chosen data sets utilize many of the same raw observations, there is a degree of interdependence.”
The chapter then states on page 51 that
“While there are fundamental differences in the methodology used to create the surface data sets, the differing techniques with the same data produce almost the same results (Vose et al., 2005a). The small differences in deductions about climate change derived from the surface data sets are likely to be due mostly to differences in construction methodology and global averaging procedures.”
and thus, to no surprise, it is concluded that
“Examination of the three global surface temperature anomaly time series (TS) from 1958 to the present shown in Figure 3.1 reveals that the three time series have a very high level of agreement.”
Moreover, as we reported in our 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.
“The raw surface temperature data from which all of the different global surface temperature trend analyses are derived are essentially the same. The best estimate that has been reported is that 90–95% of the raw data in each of the analyses is the same (P. Jones, personal communication, 2003).”
Peter Stott and Peter Thorne have deliberately misled the readership of Nature in order to give the impression that three data analyses collaborate corroborate their analyzed trends, while in reality the three surface temperature data sets are closely related.