The “Marcott Mess”

A recent paper in Science  reconstructing climate records for the Holocene received substantial media attention because it showed a gradual cooling for several thousand years followed by a dramatic uptick in temperature in the past 100 years. This uptick seemed to replicate the blade of Michael Mann’s “hockey stick,” and was highlighted in media reports on the study.  Not so fast.  In response to questions about the study’s methodology, one of the study’s authors has acknowledged that the study’s conclusions with regard to the past 100 years are not reliable.  In a “Q&A” posted on the RealClimate blog, Harvard’s Jeremy Shakun says: “the 20th century portion of our paleotemperature stack is not statistically robust, cannot be considered representative of global temperature changes.”  In other words, the study may tell us something about the Holocene, but it doesn’t tell us much of anything about the past 100 years.  But then why didn’t the press release about the study or any of the news reports on the study say so? Why didn’t the authors clarify this point with reporters until now? Roger Pielke Jr. discusses why this is important. More from Andrew Revkin here.

No, this does not show that climate change is a scientific fraud.  What it does show, however, is that some are willing to “sex up” climate science findings to feed sensational media coverage, and end up undermining confidence in climate science.  Given that there is still much we do not know about climate change — including why mean global temperature has been flat for the past ten years — undermining confidence in climate science can (further) undermine its ability to inform policy.  Climate science has taken some significant hits in the past few years.  It doesn’t need any more.