In 1998, researchers Michael Mann, Raymond Bradley and Malcolm Hughes(MBH98) conducted a paleo-reconstruction of the Northern Hemisphere temperature record. They concluded that the current NH temperature increase was anomalous in the past 1000 years.
Former mining executive and statistician Stephen McIntyre and economist Ross McKitrick criticized the work, citing flaws in the treatment of the data, and the quality of the data. Mann et al. responded, calling the criticism spurious.
The disagreement eventually made it to National Research Council of the United States National Academy of Sciences at the behest of a US Congressional investigation. Additionally, there was an independent investigation by Congressman Joe Barton, which was chaired by Edward Wegman.
The NAS report was critical of the data treatment, but essentially said they had very little effect on the overall picture. The Wegman report was more critical, citing the lack of other proxy data and questionable statistical treatment, and concluding that McIntyre and McKitrick's criticism was both "valid and compelling."
Now, since that time, there has been even more criticism of both reports, and the validity of the results from MBH98, some of it worthwhile to note, some of it not so much...
Now, a new reconstruction is available in the Proceedings of the National Academies of Science, titled "Proxy-Based Reconstructions of Hemispheric and Global Surface Temperature Variations over the Past Two Millennia", and is authored by Mann, M.E., Zhang, Z., Hughes, M.K., Bradley, R.S., Miller, S.K., Rutherford, S.
You can read it for yourself here, and the supplemental material here.
The paper is really a direct response to the criticisms of previous reconstructions.
1. The new investigation uses over-lapping proxy records, including ocean sediment, ice core, tree growth, coral growth, and borehole data, among others.
2. Without using tree-ring growth data, the results are robust to 1300 years, ie. anomalous 20th century warming.
3. The data used is of higher resolution, has much more spatial coverage than previous reconstructions.
It will be interesting to read the comments on the response of this group to the various reports.
Former mining executive and statistician Stephen McIntyre and economist Ross McKitrick criticized the work, citing flaws in the treatment of the data, and the quality of the data. Mann et al. responded, calling the criticism spurious.
The disagreement eventually made it to National Research Council of the United States National Academy of Sciences at the behest of a US Congressional investigation. Additionally, there was an independent investigation by Congressman Joe Barton, which was chaired by Edward Wegman.
The NAS report was critical of the data treatment, but essentially said they had very little effect on the overall picture. The Wegman report was more critical, citing the lack of other proxy data and questionable statistical treatment, and concluding that McIntyre and McKitrick's criticism was both "valid and compelling."
Now, since that time, there has been even more criticism of both reports, and the validity of the results from MBH98, some of it worthwhile to note, some of it not so much...
Now, a new reconstruction is available in the Proceedings of the National Academies of Science, titled "Proxy-Based Reconstructions of Hemispheric and Global Surface Temperature Variations over the Past Two Millennia", and is authored by Mann, M.E., Zhang, Z., Hughes, M.K., Bradley, R.S., Miller, S.K., Rutherford, S.
You can read it for yourself here, and the supplemental material here.
The paper is really a direct response to the criticisms of previous reconstructions.
1. The new investigation uses over-lapping proxy records, including ocean sediment, ice core, tree growth, coral growth, and borehole data, among others.
2. Without using tree-ring growth data, the results are robust to 1300 years, ie. anomalous 20th century warming.
3. The data used is of higher resolution, has much more spatial coverage than previous reconstructions.
It will be interesting to read the comments on the response of this group to the various reports.