Tuesday, 24 January 2012

Distortion by deletion

Recently there has been a thread at Skeptical Science (www.skepticalscience.com) in which they claim that Pat Michaels has distorted the science of climate change by deleting parts of figures. I hold no brief for Michaels and am not intending to comment on the accuracy or otherwise of the claims. However, if the pot is calling the kettle black it had better make sure that it is burnished and spotlessly shining. 

A few months ago I watched Michael Mann’s presentation to TEDx in November 2011, uploaded on 5 December. In it he shows a plot of the predictions of Hansen in 1988. This is from the same source as the graph from which Michaels removed two of the lines.  The following slide is from a screen dump of the presentation.

This shows Hansen’s 1988 prediction up to 2019 and observed temperatures up to 2005. Since the presentation was given in November 2011 it would have been possible to include 2010 and, to a high degree of accuracy, the likely value for 2011. In his 2006 paper Hansen also shows his projection with both “station data” and “land-ocean data”. The plot below shows observed data updated to 2011 for both observed records (the 2011 value is provisional) and Hansen's projection digitised from his 2006 paper.

When both data series are included and the data are not truncated to 2005 they tell a slightly different story.


Mike Sweet said...

As you point out, the story is "slightly different" when it is updated. It is too bad that Mann has not updated his slides, but we are all human. Pat Michaels distortion and deletion of Hansen's data shows the opposite of what the real data say. Michaels needs to remove the log from his eye before criticizing Mann for a splinter.

Administrator said...

I fully accept that the situations were different but whether by 'human error' or deliberate 'distortion' the net effect was to mislead the audience.