Broken hockey sticks

8 Jun 2012

Andrew Montford outlines what some recent activity at Climate Audit might mean - see www.bishop-hill.net/blog/2012/6/7/another-hockey-stick-broken.html (and the comments to these kind of posts are just as important as the few paragraphs that set up the response). The Mann made hockey stick was a northern hemisphere affair. We now seem to have a southern hemisphere concoction. Some 27 proxy records were used, and another 35 were looked at and rejected as unsuitable. Magically, the late 20th century emerged with unprecedented warming - although the graph appears to show a sharp spike around 1300ad. This version does not have the classic Mann made smooth handle - but it does have the sharp uptick in the 1990s. The question that is being asked - is that uptick real or is it a result of methodology, detrending, red noise, and various other kinds of revolving doors. Several things have attracted attention to Gergis et al, not least the way it seems to have been constructed for use in the upcoming IPCC report (2012/3). It also involved a put-down of Steve McIntyre by Gergis that caused him to dig around a bit and wonder why such a response was necessary. He is aided and abetted by colleagues such as Jean Sibelius and one of these enthusiastic helpers discovered Gergis had a blog - not on science but on environmentalism. Alarm bells started ringing. What was the nature of the game? After playing around it emerged the spike in the 1990s was largely due to the methodology - not to the proxy records. One of the proxies, unsurprisingly, was used upside down - not the first time this has happened and of the tricks of the 'trade' it would seem.

The IPCC intend to present a wide body of evidence and another paleoclimate record looks like it might be in favour - using similar methodology (see variously http://climateaudit.org/2012/06/04/law-dome-in-mann-et-al-2008/ and http://data.aad.gov.au and http://climateaudit.org/2012/06/06/gergis-significance)