date: Thu, 18 Jan 2007 15:49:33 -0500 from: "Michael E. Mann" subject: [Fwd: Re: British documentary about global warming] to: Gavin Schmidt , Caspar Ammann , Phil Jones guys, fyi... thanks for your advice, mike -- Michael E. Mann Associate Professor Director, Earth System Science Center (ESSC) Department of Meteorology Phone: (814) 863-4075 503 Walker Building FAX: (814) 865-3663 The Pennsylvania State University email: mann@psu.edu University Park, PA 16802-5013 http://www.met.psu.edu/dept/faculty/mann.htm Message-ID: <45AFDD20.5040101@meteo.psu.edu> Date: Thu, 18 Jan 2007 15:48:32 -0500 From: "Michael E. Mann" Reply-To: mann@psu.edu Organization: Dept. of Meteorology, Penn State University User-Agent: Mozilla Thunderbird 1.0.2 (Windows/20050317) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Eliya Arman Subject: Re: British documentary about global warming References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Dear Ms. Arman, Unfortunately I will not be available for an interview for your documentary. However, if you are interested in the true current state of affairs I suggest you contact scientists such as Caspar Ammann of NCAR and David Ritson of Stanford University, who have independently investigated the claims of our critics and shown them to be either incorrect, inconsequential, or both. You can find much relevant discussion and links to key peer-reviewed recent studies on the site "RealClimate.org". I would like to bring three main points to your attention: 1. The studies of Mann, Bradley and Hughes (1998, 1999) are more than a decade old, and a decade of more recent work by a wide range of researchers both supplants them and validates the key conclusions. Quoting from a report by the U.S. National Academy of Sciences published last summer, " The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes the additional large-scale surface temperature reconstructions and documentation of the spatial coherence of recent warming described above (Cook et al. 2004, Moberg et al. 2005, Rutherford et al. 2005, D'Arrigo et al. 2006, Osborn and Briffa 2006, Wahl and Ammann in press), and also the pronounced changes in a variety of local proxy indicators described in previous chapters (e.g., Thompson et al. in press). Based on the analyses presented in the original papers by Mann et al. and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium. " More information on the National Academy report is available here: http://www.realclimate.org/index.php/archives/2006/06/national-academies-synthesis-report/ 2. The specific criticisms of McIntyre and McKitrick (2005) have been invalidated by at least 5 different peer-reviewed studies (only 1 of which I was associated with). - Wahl and Ammann (in press) demonstrate that (a) the precise statistical conventions used in our original work have almost no influence on the end result, which is quite robust and easily replicated and that (b)each of their primary claims are seen to have been based on a number of inappropriate and erroneous procedures on their part. See: e.g. the discussion here: http://www.realclimate.org/index.php/archives/2005/05/new-analysis-reproduces-graph-of-late-20th-century-temperature-rise/ - Two additional papers by Von Storch et al and Huybers take issue with the McIntyre and McKitrick claims, discussed here: http://www.realclimate.org/index.php/archives/2005/10/hockey-sticks-round-27/ - This paper published by my collaborators and me: Rutherford, S., Mann, M.E., Osborn, T.J., Bradley, R.S., Briffa, K.R., Hughes, M.K., Jones, P.D., Proxy-based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Methodology, Predictor Network, Target Season and Target Domain, Journal of Climate, 18, 2308-2329, 2005. Discussed here: http://www.realclimate.org/index.php?p=10 and the final published version is available here at: http://www.meteo.psu.edu/~mann/shared/articles/RuthetalJClimate05.pdf The basic conclusion from these additional studies are that the claims made by M&M (2003) are either incorrect, or do not have any consequences for the conclusions of MBH98. A figure from Wahl and Amman demonstrates the non-impact of any of the legitimate issues that they may have raised quite clearly: http://www.realclimate.org/images/WA_RC_Figure1.jpg 3. The Wegman report was not the result of an impartial scientific inquiry, but was instead commissioned as part of a partisan investigation that was condemned by leading scientific organizations around the world, see e.g. the materials available here: http://branch.ltrr.arizona.edu/ http://www.geo.umass.edu/climate/bartonletter.html Neither Wegman nor anyone else associated with that report contacted me at any time. Nor did he investigate what impact changing statistical conventions had on the actual climate reconstructions. As was pointed out long ago (and emphasized by several scientists in congressional hearings last summer), such changes have an entirely inconsequential impact on the reconstruction itself. Wegman has also ignored inquiries from other scientists such as emeritus Stanford University Physics Professor David Ritson who has requested information about the calculations within the report. To my knowledge, Wegman has ignored a congressional inquiry from last year requesting such information. http://www.realclimate.org/index.php/archives/2006/08/followup-to-the-hockeystick-hearings/ http://www.realclimate.org/index.php/archives/2006/07/the-missing-piece-at-the-wegman-hearing/ Finally, I would point out that the evidence for human-caused global warming is based on many independent lines of evidence, including the fundamental physics of radiative transfer, various different types of climate observations and sophisticated comparisons of model-predicted changes with what has been observed. As mentioned above, our early studies were just one of many indicating that recent climate changes are anomalous in a long-term context, and all of these studies constitute just one of multiple lines of evidence implicating human activity for significant changes that have already been observed in the climate. From the title of this documentary, I fear that the producers do not have a proper appreciation of what science actually has to say about the issues addressed by the documentary. Sincerely, Michael E. Mann Eliya Arman wrote: >Dear Professor Mann, > >Wag TV is producing a documentary for Channel 4 called The Great Global >Warming Swindle which argues that anthropogenic Co2 is not the primary >driver of climate change. In the programme we will be featuring a >critique of your temperature record reconstruction with interviews from >Steve McIntyre, Ross McKitrick and Edward Wegman and we would like to >know whether you would like to have the chance to feature and to respond >to their criticism. > >Even though the film will be designed to present the sceptics case >strongly, we feel that it is vital that the voices of other scientists, >who believe that man-made global warming is a real threat, be present in >the film. > >It may seem like an unusual request, but I hope you might consider >granting us an interview for the documentary? > >I look forward to hearing from you. > >Yours sincerely, > >Eliya Arman > >WAG TV Ltd >2d Leroy House >436 Essex Road >London N1 3QP > >+44 (0) 207 688 2165 - t >+44 (0) 207 688 1702 - f > > > > > > > -- Michael E. Mann Associate Professor Director, Earth System Science Center (ESSC) Department of Meteorology Phone: (814) 863-4075 503 Walker Building FAX: (814) 865-3663 The Pennsylvania State University email: mann@psu.edu University Park, PA 16802-5013 http://www.met.psu.edu/dept/faculty/mann.htm