date: Tue Aug 31 13:06:22 2004
from: Mike Hulme <m.hulme@uea.ac.uk>
subject: Re: Message for Madeleen Helmer re: the January 2004 nature article
to: <e.tompkins@uea.ac.uk>,<MHelmer@redcross.nl>

   Emma and Madeleen,
   I've read the brief exchange below and Emma has asked me to comment.  There are different
   answers depending on the Qs:
   "Was the 2003 European heatwave proof that humans are altering climate?"  No, although it
   partly depends on how your audience view "proof".  If you are asking this Q a much better
   place to look for evidence ("proof") is with the global scale surface air temperature trend
   over 100+ years.  Trying to pin evidence for human influence on global climate on *any*
   discrete weather evident is a pretty poor way to proceed.  Much better is focusing on
   trends (e.g. long-term) and paramaters (e.g. global temperature) where it is easier to
   define and detect the human fingerprint in a statistical sense.  But remember, this will
   still be "statistical proof" with odds - even if small - on being wrong.  Hence IPCC's use
   of the words likely and v.likely etc.  But compare with the standard of evidence in a
   judicial system.
   "Was the 2003 European heatwave caused by human-induced climate change?"  Sorry, but this
   again is asking the wrong Q.  We are not living with a climate system where one can nicely
   separate out human-induced weather from natural weather, or at best one again might only do
   so in a purely statistical sense.  I still hold by my original view stated after the 2000
   Mozambique floods when I was publicly quoted as saying that there "is no longer any such
   thing as a natural weather event".  The global climate system is already semi-artificial
   through our perturbation of the atmosphere and so every weather event - extreme or not - is
   influenced by human actions (just as the floods in Bocastle were exacerbated by human
   intervention with the river catchment; they weren't "natural").  Of course, one can use
   clever statistical techniques to talk about likelihoods etc., but the reality is that the
   climate system is too complex for simple cause-effect relationships, or again at best one
   needs to recognise that causal explanations can co-exist at multiple levels and depending
   on which level you invoke the human influence will be more or less evident.
   In any case, why do people ask this Q?  Sure, it is good for headline grabbing and perhaps
   for public communication activities, but serious strategic planning and investment does not
   need a definitive answer to it.  For these latter applications all we need to know is the
   general direction of future trends of any given weather/climate parameter - for some
   applications this information may be needed in formal probabilisitic terms; for other
   applications much more generalised statements about increased heatwaves and more intense
   hurricanes may be sufficient.
   Is this at all useful, or can you narrow down your Q to something that needs a different
   response?
   Mike
   At 19:57 02/08/2004 +0100, you wrote:

     Hi Mike
     Could you possibly help me?  I was discussing with Madeleen Helmer
     (Director of the Netherlands Red Cross) whether or not there was yet
     conclusive proof that the heat wave last summer could be conclusively
     attributed to human-induced climate change or not (see discussion
     below).  I said that my understanding of the science is that it cannot
     as we need to have a long term trend before we can make such statements.
     Madeleen has responded below and I would very much appreciate your
     comments on this.
     Many thanks
     Emma
     PS If you think this could be a useful email discussion we could copy it
     to those who might be interested e.g. tyn.building as well as Madeleen
     and Maarten?
     -----Original Message-----
     From: Helmer, Madeleen [[1]mailto:MHelmer@redcross.nl]
     Sent: 25 July 2004 14:16
     To: e.tompkins@uea.ac.uk
     Cc: Maarten van Aalst (E-mail)
     Subject: RE: Message for Madeleen Helmer re: the January 2004 nature
     article
     Dear Emma,
     Im not a scientist but I read articles like these like I read the IPCC
     reports and alike which are also full of likelies and very likelies.
     However, a likely is very different from an unlikely. Both have a
     margin of uncertainty which is inherent to the subject and the margins
     of scientific evidence. I understand that from scientists, but when
     likelies are communicated by scientists with too much caution, the
     general public might interpret a likely as an unlikely, which too my
     view has happened in the climate change debate in the 1990-ies.
     This research and article has, to my knowledge  not been challenged as
     being unlikely. For instance the Netherlands Met office gave recently
     a presentation that confirmed these findings.
     I look forward to hear what Mike Hulme will say.
     See also a few more popular articles that came after the Nature
     publication.
     (source www.climateark.org
     Discussing the translation of scientific uncertainties to the general
     public is one of my favourite debates. So Im  looking forward to the
     continuation of this debate (and staying in touch with you in
     general...)

     best wishes,
     Madeleen Helmer
     Head Red Cross/Red Crescent Climate Centre
     Netherlands Red Cross
     PO Box 28120
     2502 KC  The Hague
     The Netherlands
     Phone: +31 (0)70 44 55 703
     Fax: +31 (0)70 44 55 712
     Cell: +31 (0)6 13 55 86 88
     E-mail: mhelmer@redcross.nl
     [2]www.climatecentre.org
     -----Oorspronkelijk bericht-----
     Van: Emma L. Tompkins [[3]mailto:e.tompkins@uea.ac.uk]
     Verzonden: woensdag 21 juli 2004 20:09
     Aan: Climatecentre
     Onderwerp: Message for Madeleen Helmer re: the January 2004 nature
     article
     Dear Madeleen
     Hello, I hope you are well and had a good trip back.  After our
     conversation I returned to the January 2004 Nature article to check my
     facts - and I thought I would paste the confusing paragraph (for me) and
     the
     concluding one below:
     1) the confusing one:
     "A conclusive analysis such as that in Fig. 2 is not feasible for summer
     2003, as there is only one data point so far off the mean. To
     quantitatively assess the situation, we have estimated its return
     period. The return period  is an estimate of the frequency of a
     particular event (or its exceedance) based on a stochastic concept. Here
     we employ a gaussian distribution fitted to JJA temperatures to estimate
     with respect to a selected reference period (see Methods section for
     details). With respect to the reference period 1864-2000, a return
     period of several million years is obtained, but such an excessive
     estimate based on a short series is dubious. To account for the warming
     in the last decades, we use a more recent reference period 1990-2002
     (with T = 1.25 C warmer mean temperature, but assuming an unchanged
     standard deviation). With respect to this climatology, the resulting
     return period for summer 2003 still amounts to  = 46,000 yr. The
     uncertainty of this estimate is considerable, however, and the lower
     bound of the 90% confidence interval is  = 9,000 yr."
     2) the concluding one:
     "Our results demonstrate that the European summer climate might
     experience a pronounced increase in year-to-year variability in response
     to greenhouse-gas forcing. Such an increase in variability might be able
     to explain the unusual European summer 2003, and would strongly affect
     the incidence of heatwaves and droughts in the future. It would
     represent a serious challenge to adaptive response strategies designed
     to cope with climate change."
     I think (not being a climate scientist) that there are still too many
     'might' and 'maybe' words in this article for me to say confidently that
     the summer of 2003 can be referred to as an indicator that climate
     change is happening.  I am going to speak to Mike Hulme about it and
     will get back to you when I have.
     Emma
     Reference
     Nature \ 427, 332 - 336 (22 January 2004); doi:10.1038/nature02300
     Nature AOP, published online 11 January 2004
     The role of increasing temperature variability in European summer
     heatwaves
     CHRISTOPH SCHR1, PIER LUIGI VIDALE1, DANIEL LTHI1, CHRISTOPH FREI1,
     CHRISTIAN HBERLI2, MARK A. LINIGER2 & CHRISTOF APPENZELLER2
     [4]http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v427/n69
     72/full/nature02300_fs.html
     --**----**----**----**----**----**----**--
     Dr Emma L. Tompkins
     Senior Research Fellow
     Tyndall Centre for Climate Change Research,
     School of Environmental Sciences,
     University of East Anglia,
     Norwich, NR4 7TJ, U.K.
     Tel: +44 (0)1603 593910
     Fax: +44 (0)1603 593901
     Email: e.tompkins@uea.ac.uk
     Web: [5]http://www.tyndall.ac.uk/research/theme3/theme3_flagship.shtml
     and
     [6]http://www.tyndall.ac.uk/research/theme4/summary_t2_42.shtml
     --**----**----**----**----**----**----**--

