I donâ€™t feel hugely energetic right now in terms of writing anything very complicated. As a simple exercise, I decided to quickly revisit the everchanging Hansen adjustments, a topic commented on acidly by E.M. Smith (Chiefio) in many posts â€“ also see his interesting comments in the thread at a guest post at Anthonyâ€˜s, a post which revisited the race between 1934 and 1998 â€“ an issue first raised at Climate Audit in 2007 in connection with Hansenâ€™s Y2K error.
As CA readers recall, Hansenâ€™s Y2K error resulted in a reduction of US temperatures after 2000 relative to earlier values. The change from previous values is shown in red in the graphic below; the figure also shows (black) remarkable re-writing of past history since August 2007 â€“ a rewriting of history that has increased the 2000-6 relative to the 1930s by about 0.3 deg C.
This impacts comparisons made in 2007 between GISS and CRN1-2 stations. At the time, it was noted that GISS adjustments for UHI resulted in the GISS US temperature anomaly having quite a bit in common with a TOBS average from Anthony’s CRN1-2 stations. Critics of Anthony’s surfacestations.org project commented on this rather smugly – too smugly given the large differences with NOAA and CRU versions in the US and the incoherence of Hansen’s adjustments outside the US. The post-2007 adjustments to GISS adjustments change this. The increased trend in the GISS US statistic comes at the expense of reconciliation with CRN1-2 stations: the trends no longer cohere.