date: Thu Jun 22 20:01:58 2006 from: Keith Briffa subject: Re: Fwd: Surface temps pdf and release to: Andy Revkin Hi Andy really short on time - stopped by office to pick up passport/tickets before leave for Bergen tomorrow am. Obviously not seen the report - hope Phil will pick up and bring. In meantime, in response to your questions At 03:47 22/06/2006, you wrote: hi keith, hope all's well. the nat academies NRC committee report on hockey stick is out as of 11 a.m. Washington time thursday. i've attached presuming you'll respect the embargo. i'm hoping you can provide some input (they cite you guys several times) on some of the lessons of this saga. if you can weigh in by quotable email by midday our time, that'd be super. feel free to pick 1 or 2 below (ideally last one, particularly)> 1) the report says the 'principal component analysis' method Mann et al used for parts of calcs is "not recommended" but goes on to say it does not seem to unduly influence results on hemisphere estimates. any idea why they concluded it is not recommended? No - and I do not necessarily agree. There are options to be chosen , as with all methods, but the latest version of the Mann et al software (REGEM) seems to work as well as other approaches , provided the input data are well dispersed and of good quality. I believe the Committee may have been premature in concluding this , as further work needs to be done (and is being done , especially involving the use of pseudo proxy data taken from model simulations). I would also add that a number of widely publicised critics of the early methods may not turn out to be as significant as previously thought . I believe we will make progress in the near future on resolving some of these debates but we do not yet know enough to jump to conclusions that may be overly dismissive of previous work. 2) they made gentle point about data sharing, but don't get specific. is this always a sticky issue? The situation is not ideal but the reasons are often to do with logistics rather than any desire to withhold data for "suspicious" reasons. 3) they have a very low confidence in any findings on pre 900 A.D. (global average) climate. fair? Yes 4) are there general lessons in the way this has played out? is it possible, in the end, to use existing proxies meainngfully back beyond a certain time span? Do not understand the question really. I certainly believe proxies can be used to provide much information for periods before the most recent millennium. However, what is lacking , ultimately, is not methodological know how, but rather a good distribution of accurate proxies, for which the uncertainties are well understood and quantified. I would be the first to acknowledge the data are relatively poor (certainly when compared to the quality and quantity of 20th century instrumental data). It is not surprising that there remain large uncertainties in our estimates of past temperature . These uncertainties are generally widely recognized. Nevertheless, I believe current interpretations of the body of evidence is generally reasonable, and it is justified to conclude that 20th century warmth is likely to be unprecedented , even over the last 1000 years, given the evidence currently to hand. To narrow uncertainties , we require much greater effort in gathering widespread data; establishing robust estimates of regional climate variability and a major effort to update and improve (by better replication) existing series of know value. finally, if the curve had not become so iconic, would we be having this discussion? Probably yes - I would not have chosen in the original TAR Summary to highlight this one curve - but we should not forget that the considerable uncertainty associated with it was shown . However it was always likely hat this curve would be challenged from a scientific point of view - as is correct - as new data and different reconstruction methods are adopted . The conclusions regarding the reality of unusual warming have certainly not been overturned since then , however. In fact, many subsequent analyses seem to reinforce this. So do not let scientific development (and sceptic misinformation ) obscure this important message. This is not to say that future work will not overturn this - but we can only conclude to the best of knowledge at any one time. thanks for helping with this, (sent a note to tim o as well) Happy for you to quote any or all of this andy Keith X-SBRS: None X-REMOTE-IP: 144.171.38.42 X-IronPort-AV: i="4.06,162,1149480000"; d="pdf'?scan'208,217"; a="11668797:sNHT1957461184" Subject: Surface temps pdf and release Date: Wed, 21 Jun 2006 12:11:09 -0400 X-MS-Has-Attach: yes X-MS-TNEF-Correlator: Thread-Topic: Surface temps pdf and release thread-index: AcaVTU7Qlxyh6OYYRdqAEXQPuz7m0w== From: "Kearney, William" To: X-NYTOriginatingHost: nat-hq-gate-01.nytimes.com, 199.181.175.221 Briefing is at 11 tomorrow here at 2100 C St. NW, hope to see you here. <> Date: June 22, 2006 Contacts: Bill Kearney, Director of Media Relations Megan Petty, Media Relations Assistant Office of News and Public Information 202-334-2138; e-mail EMBARGOED: NOT FOR PUBLIC RELEASE BEFORE 11 A.M. EDT THURSDAY, JUNE 22 'High Confidence' That Planet Is Warmest in 400 Years; Less Confidence in Temperature Reconstructions Prior to 1600 WASHINGTON -- There is sufficient evidence from tree rings, boreholes, retreating glaciers, and other "proxies" of past surface temperatures to say with a high level of confidence that the last few decades of the 20th century were warmer than any comparable period in the last 400 years, according to a new report from the National Research Council. Less confidence can be placed in proxy-based reconstructions of surface temperatures for A.D. 900 to 1600, said the committee that wrote the report, although the available proxy evidence does indicate that many locations were warmer during the past 25 years than during any other 25-year period since 900. Very little confidence can be placed in statements about average global surface temperatures prior to A.D. 900 because the proxy data for that time frame are sparse, the committee added. Scientists rely on proxies to reconstruct paleoclimatic surface temperatures because geographically widespread records of temperatures measured with instruments date back only about 150 years. Other proxies include corals, ocean and lake sediments, ice cores, cave deposits, and documentary sources, such as historic drawings of glaciers. The globally averaged warming of about 1 degree Fahrenheit (0.6 degrees Celsius) that instruments have recorded during the last century is also reflected in proxy data for that time period, the committee noted. The report was requested by Congress after a controversy arose last year over surface temperature reconstructions published by climatologist Michael Mann and his colleagues in the late 1990s. The researchers concluded that the warming of the Northern Hemisphere in the last decades of the 20th century was unprecedented in the past thousand years. In particular, they concluded that the 1990s were the warmest decade, and 1998 the warmest year. Their graph depicting a rise in temperatures at the end of a long era became known as the "hockey stick." The Research Council committee found the Mann team's conclusion that warming in the last few decades of the 20th century was unprecedented over the last thousand years to be plausible, but it had less confidence that the warming was unprecedented prior to 1600; fewer proxies -- in fewer locations -- provide temperatures for periods before then. Because of larger uncertainties in temperature reconstructions for decades and individual years, and because not all proxies record temperatures for such short timescales, even less confidence can be placed in the Mann team's conclusions about the 1990s, and 1998 in particular. The committee noted that scientists' reconstructions of Northern Hemisphere surface temperatures for the past thousand years are generally consistent. The reconstructions show relatively warm conditions centered around the year 1000, and a relatively cold period, or "Little Ice Age," from roughly 1500 to 1850. The exact timing of warm episodes in the medieval period may have varied by region, and the magnitude and geographical extent of the warmth is uncertain, the committee said. None of the reconstructions indicates that temperatures were warmer during medieval times than during the past few decades, the committee added. The scarcity of precisely dated proxy evidence for temperatures before 1600, especially in the Southern Hemisphere, is the main reason there is less confidence in global reconstructions dating back further than that. Other factors that limit confidence include the short length of the instrumental record, which is used to calibrate and validate reconstructions, and the possibility that the relationship between proxy data and local surface temperatures may have varied over time. It also is difficult to estimate a mean global temperature using data from a limited number of sites. On the other hand, confidence in large-scale reconstructions is boosted by the fact that the proxies on which they are based generally exhibit strong correlations with local environmental conditions. Confidence increases further when multiple independent lines of evidence point to the same general phenomenon, such as the Little Ice Age. Collecting additional proxy data, especially for years before 1600 and for areas where the current data are relatively sparse, would increase our understanding of temperature variations over the last 2,000 years, the report says. In addition, improving access to data on which published temperature reconstructions are based would boost confidence in the results. The report also notes that new analytical methods, or more careful use of existing methods, might help circumvent some of the current limitations associated with large-scale reconstructions. The committee pointed out that surface temperature reconstructions for periods before the Industrial Revolution -- when levels of atmospheric greenhouse gases were much lower -- are only one of multiple lines of evidence supporting the conclusion that current warming is occurring in response to human activities, and they are not the primary evidence. The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering. It is a private, nonprofit institution that provides science and technology advice under a congressional charter. A committee roster follows. Copies of Surface Temperature Reconstructions for the Last 2,000 Years will be available from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at [1]http://www.nap.edu. Reporters may obtain a pre-publication copy from the Office of News and Public Information (contacts listed above). [ This news release and report are available at [2]http://national-academies.org ] NATIONAL RESEARCH COUNCIL Division on Earth and Life Studies Board on Atmospheric Sciences and Climate Committee on Surface Temperature Reconstructions for the Past 2,000 Years: Synthesis of Current Understanding and Challenges for the Future Gerald R. North (chair) Distinguished Professor of Meteorology and Oceanography and Harold J. Haynes Endowed Chair in Geosciences Texas A&M University College Station Franco Biondi Associate Professor of Physical Geography University of Nevada Reno Peter Bloomfield Professor of Statistics and of Financial Mathematics North Carolina State University Raleigh John R. Christy Professor of Atmospheric Science, and Director Earth System Science Center University of Alabama Huntsville Kurt M. Cuffey Professor of Geography University of California Berkeley Robert E. Dickinson^1,2 Professor School of Earth and Atmospheric Sciences Georgia Institute of Technology Atlanta Ellen R.M. Druffel Professor of Earth System Science University of California Irvine Douglas Nychka Senior Scientist National Center for Atmospheric Research Boulder, Colo. Bette Otto-Bliesner Scientist Climate and Global Dynamics Division; Head Paleoclimate Group; and Deputy Head Climate Change Research Section National Center for Atmospheric Research Boulder, Colo. Neil Roberts Head School of Geography University of Plymouth Plymouth, United Kingdom Karl K. Turekian^1 Sterling Professor of Geology and Geophysics Yale University New Haven, Conn. John M. Wallace^1 Professor of Atmospheric Sciences, and Director Joint Institute for the Study of the Atmosphere and Ocean University of Washington Seattle RESEARCH COUNCIL STAFF Ian Kraucunas Study Director ^ ^1 Member, National Academy of Sciences ^2 Member, National Academy of Engineering Bill Kearney Director of Media Relations Office of News & Public Information The National Academies 2101 Constitution Ave. NW #182 Washington, DC 20418 202-334-2144 [3]wkearney@nas.edu ANDREW C. REVKIN The New York Times / Environment 229 West 43d St., NY NY 10036 phone: 212-556-7326 / e-mail: revkin@nytimes.com / fax: 509-357-0965 Arctic book: The North Pole Was Here: [4]www.nytimes.com/learning/globalwarming Amazon book: The Burning Season [5]www.islandpress.org/burning Acoustic-roots band: [6]www.myspace.com/unclewade -- Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 [7]http://www.cru.uea.ac.uk/cru/people/briffa/