No single topic seems to arouse as much blog animosity as any discussion of Hansen’s projections. Although NASA employees are not permitted to do private work for their bosses off-hours (a currying favor prohibition, I suppose) - for example, secretaries are not supposed to do typing, over at realclimate, Gavin Schmidt, in his “private time”, which flexibly includes 9 to 5, has provided bulldog services on behalf of his boss, James Hansen, on a number of occasions.

In January 2008, I discussed here and here how Hansen’s projections compared against the most recent RSS and MSU data, noting a downtick which resulted in a spread not merely between observations and Scenario A, but between observations and Scenario B, sometimes said to have been vindicated. For my January 16, 2008 post, I used the then most recent RSS data (as well as UAH version which showed a lesser downtick. However, a few days later, RSS revised their data to be more in line with UAH. On January 23, 2008, I updated my graphic, using the revised RSS data, which caused a slight modification. Some blog commentators have suggested that I had made in error in my Jan 16, 2008, but these suggestions have no purpose other than defamation. I had used the then current data and promptly updated my graphic within a few days of RSS revising their data. In the latter post, I criticized RSS for not issuing a notice of the change.

In a post today, Andrew Bolt used the earlier version of this graphic from January 16, 2008, rather than the January 23, 2008. A couple of blog commenters have criticized Bolt for using the earlier graphic, with Tim Lambert additionally criticizing me for not having placed a notice of the update on the Jan 16, 2008 post (which I’ve now done.)

However, rather than engaging in further exegesis of the January versions, I thought it would be useful to update the graphics to include satellite data up to June 2008 and GISS data up to May 2008. Ironically, the new data has resulted in a downtick that is more substantial than either of the versions published in January. Lucia has also done many posts on this topic and I urge readers to visit her blog.

I’m going to post up a few different versions in order to forestall pettifogging about provenance as much as possible. On the top left is May 2007 graphic comparing observed versus actual from Hansen bulldog Gavin Schmidt (which I also showed in my Jan 16, 2008 post). On the top right is Hansen projections (realclimate version plotted against monthly GISS GLB to May 2008), both in native units (1951-1980 for GISS GLB; Hansen forecasts seem to have a similar centering). On the bottom left is the same for GISS land only and on the bottom right the same for RSS satellite. RSS satellite is a bit lower than GISS, but the effect is the same.) I’ve re-centered RSS to match GISS GLB on 1979-1997.

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