Sunday, January 15, 2012


date: Tue, 06 Jul 1999 15:33:18 +0100
from: Frank Oldfield <>
subject: Impact Assessment.

Dear keith,

Hope all is going well for you. Rick suggested I pass this harangue of mine
on to you. I've shrtoened it a bit (believe it or not). It reflects more
frustration than inspiration, but if it rings any bells with you, maybe it
is worth not forgetting:

"The more I listen to the current crop of Integrated Impact Assessment
(IIA) and related stuff (I volunteered for another stiff dose at the Boston
AGU and held on up to the point when aversive therapy kicked in), the more
impatient I get. With very few if any exceptions, they fail to make
adequate or intelligent use of the paleorecord even if they show any
awareness of it at all. If we really believe in what we increasingly see as
shifts in modes of variability/ extremes beyond the instrumental
record/human activity-climate variability interactions/ non-linear and
relatively irreversible responses to threshholds etc etc all from evidence
that lies beyond the range of instrumental records we should be pushing
harder to make the IIA community attracted to and interested in making use
of what we have to say.

It seems to me that one way to break in would be through the current
concerns for sustainability and food security etc. What seems mostly to
happen at present is the development of scenarios from coupling three kinds
of model:

(i) GCM-based climate projections reflecting 2XCO2 or whatever, downscaled
in some way to regional level, or alternatively, synthetic climate
variability produced by a weather generator type of model.
(ii) crop models based on physiology etc.
(iii) socio-economic models which themselves aim to couple macro
(national/international) influences and small scale (eg.individual farmer)
decision making processes.

There's not much we can do about (ii) or (iii), but we can at least ask
ourselves whether there is any alternative to (i). As I see it, future
climate scenarios are pretty ropey at global scale anyhow and they do
precipitation and moisture balance (key properties for crops etc) badly
relative to the level of confidence needed. Once they get downscaled to
regional level, they are worse. The alternative approach, to use 'weather
generator' type modelling capability, may be better in some ways, but
relies entirely on relatively short instrumental records at best as far as
I can discover. In my view, the key 'strengths' of this kind of approach
are (i) the relative fluency with which scenarios can be developed (ii)
total lack of any way in which they can be tested except in real time (by
which time it is too late and one can always claim a new and better model
is now available that accommodates the problems that screwed up the last
one) (iii) existence of a powerful priesthood with a vested interest in the
whole business. NOTE - these are exactly the very characteristics that kept
the Oracle at Delphi in business and my best guess is that those Greek
ladies probably did better though the odd war went astray!

Contrast the above with paleodata which gets better at the region specific
level and actually measures reality. If we look at Golbal or
pan-Hemispheric reconstructions of climate variability over the last few
centuries, the amplitude of decadal or century scale variation falls short
of that projected for the next century, so perhaps it is difficult to push
the idea that on that spatial scale future scenarios can be effectively
fuelled by paleodata. But if we look at regional level, the variations are
aften larger and for extreme years/seasons/events - whether they actually
occur serially or not - it is often possible to develop credible synoptic
situations linked to the phenomena. If then we think about future
scenarios not as changes in hypothetical means but as changes in the
frequency and persistence of documented 'anomalies' we can generated
scenarios that are both based on reality and make use of the full range of
variability we can reconstruct. Of course this approach too has its flaws
and limitations, since future forcing may generate weather patterns etc.
outside the range of past extremes and so forth, but I do not think these
flaws are anything like so severe as the ones that afflict the other

The big question is ' is there anything we can do about this?' .

What I feel we really need are contacts at the potential 'user' end who are
neither locked into promoting climate scenario/model development for their
own advantage nor closed minded to the possibility that other appraoches
could be useful.

Any ideas?


Frank Oldfield

Executive Director
Barenplatz 2
CH-3011 Bern, Switzerland


Phone: +41 31 312 3133; Fax: +41 31 312 3168

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