I wrote a program to plot temperature data a while ago, although it's from the GHCN rather than the HadCRUT4 data set. https://code.google.com/p/tempgraph/ htt

I wrote a program to plot temperature data a while ago, although it's from the GHCN rather than the HadCRUT4 data set. https://code.google.com/p/tempgraph/ https://code.google.com/p/tempgraph/ The square gridding method which they appear to have used in HadCRUT4 introduces problems with singularities, but even with a better gridding method the anomaly results are broadly in line with the conventional view about global warming.