A Reconstruction of Regional and Global Temperature for the Past 11,300 Years
Exceptional Now
Abstract
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RE: 'Exceptional Now'
The 'Exceptional now' paragraph suggests that current temperatures are warmer than 90% of the Holocene. This is at odds with the abstract and paper itself that suggests current temperatures are warmer than 75% of the Holocene.
RE: Present temp date of "wheelchair" graph created by Jeremy D. Shakun
The excellently done "wheelchair" graph shows a blue line. http://www.antarcticglaciers.org/glaciers-and-climate/climate-change/
1. What is the last date of the Present temperature data shown at the right hand side of the graph in blue? "Present" is used by different authors as different dates. For example, for Greenland ice cores, BP starts at 1950 and their graphs end at -95 BP. I am trying to distinguish between actual temp data used and the temp projections shown in orange.
2. Am I correct that the difference in temp minimum in the wheelchair graph 20,000 years ago and the frequently seen Greenland ice core graph is due to the actual temp difference between Greenland and your much more global temperature sources?
RE: Comment on Marcott et al 2013
This comment was originally posted on the old version of the Science website in March 2013.
Brief comment on "A Reconstruction of Regional and Global Temperature for the Past 11,300 Years"
Paul Matthews, School of Mathematical Sciences, University of Nottingham, UK
16 March 2013
This paper includes several graphs that show slow temperature variation over the last 10000 years followed by a rapid rise over the 20th century. This aspect of the paper has unsurprisingly been seized upon enthusiastically by climate activists and journalists. However it is clear that this result is spurious. Note the following points:
1. The proxy data in the accompanying Excel file show no dramatic increase in the 20th century. This can easily be checked simply by plotting the supplied data.
2. Figures S5 and S6 show no recent upturn at all.
3. The Phd thesis of the first author uses the same data sets and plots similar graphs, but with no trace of any sharp increase. This earlier contradictory work is not cited in the paper.
4. The supplementary material provides no explanation for how the graphs were constructed. Carrying out an averaging of the proxy data yields a graph similar to that in the thesis, quite different from that in the paper. Why was no detailed explanation of the procedure reported? Will the authors supply the code that was used?
Any one of these issues would raise serious questions about the validity of this work. Taken together they leave no doubt that the results presented are spurious and misleading. The paper should be withdrawn immediately. The fact that such an obviously flawed paper was published raises serious questions about the authors, the quality of the refereeing process and the handling of the paper by the editors of Science.