Tuesday, September 02, 2008

Hockey Stick revived

Michael Mann's controversial "hockey stick" reconstruction of the historical climate has been relaunched, under slightly unusual circumstances. While press releases and in some cases further details have been sent to sympathetic bloggers and news outlets, his actual paper hasn't been published yet and no data has been released. This makes it impossible for anyone of an analytical bent to assess how valid his new reconstruction is.

This of course gives alarmists a free run while the more considered commentators have to wait to see how valid the work really is. Last time, it wasn't valid.

All that can really be said so far, from graphs released so far, is that one of the most debatable aspects of the original seems to have remained in place. The graph is unexceptional when it consists just of proxy data, but then at the end an instrument-derived bit is tacked on and this, and apparently this alone, produced the twentieth-century spike that gives the graph its name.

2 comments:

dearieme said...

Apart from the demolition of the number-fudging methods he used to resolve proxy data into the time-profile he wanted to get, there was another weakness in his previous stunt. The data (plural for some of us codgers) from bristlecone pines have been exploded. Problems include (1) pine growth rings are anyway a lousy proxy for temperature - they probably respond more to rainfall, and (2) you can hike to the actual bristlecones, inspect them, resample them, and then point out deficiencies in the data. So one wants, does one not, some proxy data than critics will find it much harder to find fault with. Ice cores sound good - the buggers can't hike up to them, eh?

dearieme said...

P.S. I wouldn't buy a second-hand hockey stick from that Mann.