Hockey Stick: The Usual Scoundrels
The National Academy of Sciences has released its study of Surface Temperature Reconstructions for the Last 2,000 Years (2006) which can be read online here. Lubos Motl has assembled a collection of critiques by the usual scoundrels and liars. (He also has a link that purports to be to the NAS report, but is in fact just commentary by a highly biased commentator.)
Let me recapitulate what I know of a key background controversy: Mann, Hughes, and Bradley (MHB)published the "hockey stick" paper with a reconstruction of the past millenium's climate which showed the hockey stick shape, with the present as blade of the stick. Subsequently, McIntire and McKittrick (M&M)critiqued their reconstruction, had some difficulty getting their critique published, and name calling ensued. Other climatologist and statisticians subsequently weighed in on both sides of the issue. Because Mann et. al. claimed that their reconstruction showed that the present was the warmest period in the last 1000 years, this became a cause celebre for the anti-global warming guys.
The NAS was asked to examine the whole subject of climate reconstructions, and the report linked to above is the result. As should be the case in an NAS study, the importance of the report lies less in their conclusions than in their careful presentation of the issues. Those conclusions point out certain defects in the arguments of each side.
M&M argued that MHB's statistical methodology was flawed, and that a better methodology (theirs) showed considerable uncertainty about the reconstructed temperatures more than 500 years ago. The National Academy's analysis concludes that they and other critics of MHB have a point, but also say that it's not possible to conclude which statistical analysis is best because (among other things) different measures of uncertainty are sensitive to different kinds of uncertainties in the data. Most relevantly to the HS controversy, they conclude that there is considerable certainty to the conclusion that the present is the hottest period in the last 400 years, but that the same cannot be concluded about the last 1000 years.
That they conclude, does not imply that attempting to reconstruct past climates is a bad idea, nor does it contradict the evidence that our current warming is mainly anthropogenic in origin. The limitations of the available evidence don't make it possible to conclude what caused the medieval warming (or even if it really happened), but we have a lot more information about the present.
Personally, I always considered this debate rather peripheral to the whole issue of anthropogenic climate change (how much does it matter if the present is the warmest time in the last 400 years or the last 1000?) but this is apparently a partial vindication for M&M and a less than full vindication for MHB. The important question, from my point of view is not our uncertainty about what happened 1000 years ago, but what is likely to happen in the next 50 to 100 years.
Let me recapitulate what I know of a key background controversy: Mann, Hughes, and Bradley (MHB)published the "hockey stick" paper with a reconstruction of the past millenium's climate which showed the hockey stick shape, with the present as blade of the stick. Subsequently, McIntire and McKittrick (M&M)critiqued their reconstruction, had some difficulty getting their critique published, and name calling ensued. Other climatologist and statisticians subsequently weighed in on both sides of the issue. Because Mann et. al. claimed that their reconstruction showed that the present was the warmest period in the last 1000 years, this became a cause celebre for the anti-global warming guys.
The NAS was asked to examine the whole subject of climate reconstructions, and the report linked to above is the result. As should be the case in an NAS study, the importance of the report lies less in their conclusions than in their careful presentation of the issues. Those conclusions point out certain defects in the arguments of each side.
M&M argued that MHB's statistical methodology was flawed, and that a better methodology (theirs) showed considerable uncertainty about the reconstructed temperatures more than 500 years ago. The National Academy's analysis concludes that they and other critics of MHB have a point, but also say that it's not possible to conclude which statistical analysis is best because (among other things) different measures of uncertainty are sensitive to different kinds of uncertainties in the data. Most relevantly to the HS controversy, they conclude that there is considerable certainty to the conclusion that the present is the hottest period in the last 400 years, but that the same cannot be concluded about the last 1000 years.
That they conclude, does not imply that attempting to reconstruct past climates is a bad idea, nor does it contradict the evidence that our current warming is mainly anthropogenic in origin. The limitations of the available evidence don't make it possible to conclude what caused the medieval warming (or even if it really happened), but we have a lot more information about the present.
Personally, I always considered this debate rather peripheral to the whole issue of anthropogenic climate change (how much does it matter if the present is the warmest time in the last 400 years or the last 1000?) but this is apparently a partial vindication for M&M and a less than full vindication for MHB. The important question, from my point of view is not our uncertainty about what happened 1000 years ago, but what is likely to happen in the next 50 to 100 years.
Comments
Post a Comment