Thursday, June 14, 2012

5170.txt

date: Tue Aug 31 13:06:22 2004
from: Mike Hulme <m.hulmeatXYZxyz.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.tompkinsatXYZxyz.ac.uk
Cc: Maarten van Aalst (E-mail)
Subject: RE: Message for Madeleen Helmer re: the January 2004 nature
article
Dear Emma,
I�m 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 I�m 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: mhelmeratXYZxyzcross.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 SCH�R1, PIER LUIGI VIDALE1, DANIEL L�THI1, CHRISTOPH FREI1,
CHRISTIAN H�BERLI2, MARK A. LINIGER2 & CHRISTOF APPENZELLER2
[4]http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v427/n69
72/full/nature02300_fs.html
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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.tompkinsatXYZxyz.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
--**----**----**----**----**----**----**--

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