|2010-11-20 16:49:18||NASA GISS adjustments, rewriting mid-century cooling etc – any info, anyone?|
When I was researching the claims being made about Climategate, I kept coming across claims that GISTEMP is not an independent confirmation of CRU’s results because they keep changing their data from earlier decades to “rewrite mid-century cooling”. For example, they point to an old article in Newsweek where the (at that time very preliminary) analysis shows a dramatic cooling from the 1940s to the 1970s.
It would be good to be able to refute this argument because it is used to claim that GISTEMP is no better than CRUTEM. I’m pretty confident that the changes in the trends over time have more to do with GISS having expanded their coverage to the southern hemisphere than the fabrication of these paranoid imaginings, but how can we check this?
I don't have anything on any changes GISTEMP may have made, but this paper is interesting wrt the change from warming to cooling in the mid 40's. http://www.atmos.colostate.edu/ao/ThompsonPapers/ThompsonWallaceJonesKennedy_JClimate2009.pdf
Essentially their analysis seems to suggest that a sudden change in the proportion of British vs American ships collecting SST data in Aug' 1945 may indicate that the warming prior to 1945 is somewhat over stated while the cooling post 1945 may be similarly overstated. The two nations used different 'technology' to measure water temps, and that there is an old instrumentation problem.