crickham said- I stumbled upon this paper that analyzes GISS algorithms for homogenizing temp data and removing urban bias. I thought you might like to read it. it certainly clears up quite a few of the adjustments and the methods for doing so. http://oprj.net/oprj-archive/climate-science/31/oprj-article-climate-science-31.pdf I, for one, have always been suspicious of new figures for old readings. this really is the oddest part. why does GISS basically stop adjusting after 1990? this paper really is amazing. I recommend it for anyone who wants to know more about the nuts and bolts of how global temp datasets are made.