Obfuscating data presentation in Vose et al 2005

This paper in GRL, "An intercomparison of trends in surface air temperature analyses at the global, hemispheric, and grid-box scale",  Russell S. Vose, David Wuertz, and Thomas C.Peterson Climate Analysis Branch, National Climatic Data Center, Asheville, North Carolina, USA P. D. Jones Climatic Research Unit, University of East Anglia, Norwich, UK, in my opinion fails miserably if its purpose was to convey clearly to readers, the realities of  the extent of  differences and agreements between the GHCN and CRU global datasets.
Dowload the pdf version of Vose et al 2005.
The very significant differences between GHCN and CRU T datasets portrayed on our full size global map should be remembered  next time anybody reads/hears  IPCC propaganda to the effect that, "the science is settled",  or "the global temperature datasets are in agreement"

	Early last year a small group of us noticed that in the Vose et al Fig 5 paired global maps of GHCN and CRU trends 1976-2003, there were many grid points greatly different in one map compared to the other. Vose et al provide two examples of discrepancies “to illustrate the typical causes involved”.  The first, centred over the southern tip of the Baja California, involves a trend difference of 0.776 degrees per decade.  This means that, over this part of the earth, the CRU series exhibits a temperature trend that is 2.10 degrees higher than shown by the GHCN over the period 1976-2003. “The second problematic box” addressed by Vose et al is centred near southern California (incl L.A.), which has one of the densest networks of high-quality temperature measurement stations in the world.  Here there is a large discrepancy in the opposite direction.  The GHCN record has trend warming of 0.796 degrees per decade higher than the CRU record, or 2.15 degrees over the period of record. We tried to obtain station data for CRU so we could assist the authors of Vose et al with our analysis but were denied the station data.
	Then studying Fig 6 we began pondering the Vose et al statement in their section 4 [14] that, "..9.4% of all grid-box trends differ by more than 0.100 [degree C per decade] in both magnitude and sign." It soon became clear that this clever use of the calming number 9.4% was in fact concealing the fact that a vastly greater number of grid points varied by more than 0.1 degree C per decade, regardless of sign. Vose et al are trying to show that GHCN and CRU are similar, so it does not matter if for any grid point one or the other is higher, it is DIFFERENCE that is the issue, so sign is a red herring.
	Last year we obtained a file of the various global grid point trends re Fig 5 from Russell Vose and found that in fact a staggering 57% of grid points differed by more than 0.1, either + or -. So, 57% of grid points differ by greater than the magnitude of century long global warming. It looks to me as though any agreement between GHCN and CRU at the grid point level over the period 1976-2003 is simply due to the sum of all errors tending to approach zero. North America would have the largest area of high quality climate data on earth, yet look at the stunning differences in many grid cells. Click on the USA for  our Global map.

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7 March 2007