date: Thu Jun 22 20:01:58 2006
from: Keith Briffa <k.briffa@uea.ac.uk>
subject: Re: Fwd: Surface temps pdf and release
to: Andy Revkin <anrevk@nytimes.com>

   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

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     Subject: Surface temps pdf and release
     Date: Wed, 21 Jun 2006 12:11:09 -0400
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     From: "Kearney, William" <WKearney@nas.edu>
     To: <revkin@nytimes.com>
     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.
     <<STR Prepub.pdf>>
     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 <news@nas.edu>
     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/

