Tuesday, May 15, 2012

4225.txt

cc: m.hulme@uea.ac.uk, parryml@aol.com, steve smith <ssmithatXYZxyz.gov>, s.raper@uea.ac.uk, Tsuneyuki MORITA <t-moritaatXYZxyzs.go.jp>, tim.carteratXYZxyz.fi
date: Mon, 27 Aug 2001 14:16:16 -0600
from: Tom Wigley <wigleyatXYZxyzr.edu>
subject: Re: TGCIA scenario recommendations
to: Rob Swart <Rob.SwartatXYZxyzm.nl>



Rob Swart wrote:
>
> Dear Tom,
>
> Thanks for your message and papers. The problem is clearly one of the
> science-policy interface. If science cannot demonstrate that it makes a
> difference in terms of avoided climate change and impacts if GHG
> concentrations are stabilised, why bother?

I'M SURE THAT THIS IS JUST A RHETORICAL QUESTION -- BUT HERE IS A SIMPLE
ANSWER NEVERTHELESS. IT IS LIKE DRIVING A HEAVY CAR WITH POOR BRAKES
DOWN AN UNFAMILIAR ROAD IN MOUNTAINOUS TERRAIN. THERE MAY BE NOTHING
SERIOUS IN SIGHT, BUT SOME FINITE (BUT POORLY DEFINED) PROBABILITY OF A
ROCK FALL OR CLIFF OR OTHER DANGER OUT OF SIGHT. SINCE THE CAR HAS
LARGE INERTIA, IF WE PUT THE BRAKES ON, WE WILL NOT SEE A RAPID
RESPONSE. THE TRICKY QUESTION IS JUST WHEN AND HOW HARD TO PUT THE
BRAKES ON.

Currently a Danish guy, Bj�rn
> Lomborg, is making the headlines again (Guardian, New York Times,
> Economist), TV programmes, etc.) telling the public (and policymakers) not
> only that there aren;'t any environmental problems, but also, even if
> climate change may be real, it does not make any sense at all to do
> something about it, since efforts to control GHG emissions are expensive
> and the mitigation would not make any difference at all anyway in terms of
> avoiding negative consequences. Very popular message.

AND A MUCH MORE COMMON ONE HERE IN THE USA. DIFFICULT TO DEAL WITH.

Now clearly,
> scientists should clearly explain what they can say about this issue. My
> expectation would indeed be that comparing climate changes resulting from
> reference cases and from stabilization cases would not be distinguishable
> until well into the 2nd half of the century (like in the GRL paper), but if
> this is so, so be it.

YES -- BUT A LOT OF PEOPLE DON'T EVEN REALIZE THIS.

2050 seems a lot closer now in 2001 (2050 is THIS
> century and our childrens' lifetime) than it was in 1999 (when 2050 was
> something of the next century and some abstract next generations). It is a
> matter of communication skills to get the message across about the long
> timescales and inertia of the systems involved, and the difficulty of
> identifying the climate change signal in the noise of natural variability.

OF COURSE -- HAVEN'T WE BEEN SAYING THIS FOR YEARS? I CERTAINLY HAVE.
UNFORTUNATELY, THE MESSAGE DOESN'T GET ACROSS TO THE RIGHT PEOPLE.

> I would be curious what your opinion is about the UK work of Nigel Arnell,
> Martin Parry, John Mitchell and others, analysing the (significant) avoided
> impacts of 550 stabilisation from an IS98a reference.

I PRESUME YOU MEAN IS92a, NOT IS98a. I HAVE NOT SEEN THIS WORK, BUT I
NOTE FOUR THINGS: (1) NONE OF THESE THREE PEOPLE ARE ECONOMISTS; (2) IF
THIS IS BASED IN ANY WAY ON THE HADLEY CTR'S GRL PAPER ON STABILIZATION,
THEN IT IS LIKELY TO BE FLAWED BECAUSE THE CALCULATIONS IN THAT PAPER
WERE TOO IDEALIZED; (3) MY OWN WORK COMES TO A DIFFERENT CONCLUSION; (4)
THE ISSUE IN ANY EVENT IS COST OF MITIGATION VERSUS BENEFITS OF REDUCED
CLIMATE CHANGE.

Another strategy of
> concerned scientists may be not to do these analyses at all in order to
> avoid a possible result that the differences between reference and
> stabilisation can not be demonstrated in a scientifically credible and
> unambiguous way and hence climate policy action may be obstructed. To me,
> this does not seem to be the honest way to go.

I AGREE COMPLETELY. EVEN IF SOME PEOPLE COP OUT, *SOMEONE* WILL DO THE
WORK. IT JUST HAS TO BE CAREFULLY PACKAGED.

>
> I am not sure what this all implies for the planned recommended
> stabilization runs. Your points about the climate sensitivity and non-CO2
> gases are well taken. I am not sure the sulfur emissions in the proposed
> post-SRES scenarios would make a lot of difference, since already in the
> SRES base cases sulfur emissions are pretty low, and these would only be
> slightly different (usually lower) in the stabilisation cases.

THE RESULTS I USED IN THE STABILIZATION PREPRINT PAPER USED MiniCAM TO
ESTIMATE THE CONCOMITANT EFFECTS ON SO2 OF CO2 STABILIZATION AT 550ppm.
ARE YOU SAYING THAT MiniCAM IS RADICALLY WRONG? I DOUBT IT. OF COURSE,
THIS SHOULD BE (AND I BELIEVE IS BEING) DONE WITH A BUNCH OF MODELS; BUT
I AM WILLING TO BET THAT MY RESULTS ARE QUALITATIVELY CORRECT.

You suggest
> "carefully constructed idealized scenarios". Do you mean carefully
> constructed from the climate system point of view in order to get
> "distinguishable results", or carefully constructed from the socio-economic
> point of view so as to analyse real-world consistent and plausible futures
> (the latter is what Morita's exercise tried to achieve)? My answer would
> be: both.

YES -- THAT IS EXACTLY MY POINT. FROM WHAT I CAN SEE (AND MY APOLOGIES
IF THIS IS WRONG) NOT ENOUGH CLIMATE EXPERTISE HAS GONE INTO THE
ECONOMIC WORK SO FAR -- I AM ARGUING FOR BETTER COMMUNICATION.

>
> I'd like to reflect a little bit more on this and since I am a scenario
> expert rather than a climate expert, await reactions from people more
> expert in the area of climate modelling, like Sarah, Mike and Tim, and
> Martin himself as chair of the TGCIA.

MANY THANKS FOR THIS QUICK RESPONSE. THESE ARE DIFFICULT ISSUES.

>
> Thanks again,
>
> Rob
>
>
> Tom Wigley
> <wigley@ucar. To: Rob Swart <Rob.SwartatXYZxyzm.nl>
> edu> cc: parryml@aol.com, tim.carter@fmi.fi, m.hulme@uea.ac.uk,
> s.raper@uea.ac.uk, Tsuneyuki MORITA <t-moritaatXYZxyzs.go.jp>, steve smith
> 25-08-01 <ssmithatXYZxyz.gov>, (bcc: Rob Swart/RIVM/NL)
> 01:47 Subject: Re: TGCIA scenario recommendations
> Please
> respond to
> wigley
>
>
>
> Rob and others,
>
> The key thing with doing stabilization runs with AOGCMs is (as Rob says)
> that the different cases "would have to be distinguishable from one
> another". This is the crux of the problem (in fact, it is a non-trivial
> problem even to define what is meant by "distinguishable from one
> another").
>
> A few years ago we decided to try to do some matched no-climate-policy
> and (550ppm) stabilization runs where the two scenarios had some
> semblance of realism. (It turns out that the only similar work is that
> done by the Hadley Ctr, but the scenarios they used are highly
> idealized.) Our runs were also idealized in that we only changed CO2 --
> in the best scientific tradition of changing only one thing at a time to
> assess sensitivities. The first results of our exercise (using CSM) are
> in Dai et al., J. Climate 14, 485-519, 2000. A number of things were
> clear from this. First, one cannot tell much from single realizations of
> the two cases -- ensemble runs are essential. Second, as we already knew
> from running simple models, the no-policy and stabilization runs diverge
> only slowly. Even after 50 years, the two are only just distinguishable
> at the global-mean level; so, clearly,differences at the regional level
> (especially for precipitation) would not be detectible above the noise
> of natural variability.
>
> So our next step was to do ensembles of 5, this time using PCM instead
> of CSM (this paper is in press in BAMS -- for a pdf preprint, look at
> www.cgd.ucar.edu/cas/adai/). Even then, for ensemble means, the
> separation between the no-policy and stabilization cases is slow. So I
> devised an extended no-policy case out to 2200 (50 years beyond where
> the CO2 level stabilizes in the stabilization run), and we extended some
> of the runs out to 2200. This work is in press in GRL (and downloadable
> from the above site). Additional important results come from these
> experiments. One important result is that, even for precipitation, the
> *patterns* of change are not detectibly different between the no-policy
> and stabilization runs. A second important result is that, for most of
> the world the intra-ensemble differences are similar to or greater than
> the underlying signals of change. Distinguishing the no-policy and
> stabilization runs therefore presents a much greater challenge than any
> of you probably realize.
>
> There are two issues to keep in mind, however. The first is that PCM and
> CSM have quite low climate sensitivities. So, will things be different
> if one used a more sensitive model? I suspect not in any major way. The
> reason is because inter-annual variability tends to be higher in more
> sensitive models, so the signal-to-noise ratio may not change much. This
> also applies to the intra-ensemble noise, since the root cause of these
> intra-ensemble differences is the internal variability of the model.
>
> The second issue is that we have only changed CO2 in our experiments. We
> know that attempts to stabilize CO2 via emissions reductions also affect
> SO2 emissions -- so perhaps the no-policy and stabilization cases might
> be more distinguishable if one accounted for these concomitant SO2
> effects? I have addressed this issue at the global-mean level in a paper
> on stabilization that I will attach to this email. (A more extensive
> analysis is in another paper, with Steve Smith as my co-author, that I
> am not ready to share with anyone just yet.) My judgment, as someone
> with quite a lot of experience in this area, is that having full spatial
> details will not make the problem any easier; since, as the spatial
> scale is reduced so the noise increases.
>
> My recommendation from all this is that, first, you read the attached
> paper (and I would welcome feedback on this) and the three
> above-mentioned Dai et al. paper. Then, you might want to re-consider
> what your strategy should be. In my view, I do not think we as a
> community are at the stage where we can blindly develop paired no-policy
> and stabilization scenarios and simply feed them into AOGCMs to see the
> consequences. I believe that carefully constructed idealized scenarios
> (perhaps based on what Morita is doing) will provide much more useful
> information. You are already probably well aware of the need to do
> ensemble runs, and I don't need to remind you how computationally
> expensive this can be.
>
> I hope these comments, and the papers, are useful. I'm sorry that it is
> impossible for me to come to the Barbados meeting, but I am willing to
> help in any way that I can.
>
> Best wishes (and good luck), Tom.
> ********************************
>
> Rob Swart wrote:
> >
> > Dear Sarah, Tom, Tsuneyuki, Martin, Mike and Tim,
> >
> > Back from holidays I found your email exchange. Let me first apologize
> that
> > I did not inform Sarah about this TGCIA action. I remembered from the
> > IPCC-TGCIA meeting ? apparently wrongly - that Mike and/or Tim would
> inform
> > Sarah, as they would be in touch with her anyway (I did not even have
> > Sarah's email address at the time). Let me also reiterate the reason for
> > Tsuneyuki's invited proposal. In order to have comparable GCM results
> > available and impact studies based on these results at the time of the
> IPCC
> > Fourth Assessment Report, and taking into account that GCM teams are
> > unlikely to perform dozens of runs, the IPCC-TGCIA (chaired by Martin)
> > intends to recommend a limited set of both baseline and stabilization
> > scenarios for such runs. In this way, impact modellers in the coming
> years
> > could base their analysis on different runs from different GCMs for the
> > same socio-economic scenario(s). Evidently, teams are free to run
> whatever
> > scenario they think interesting, but comparability would be preferable,
> and
> > many teams have proven responsive to IPCC-TGCIA recommendations in the
> past
> > as I understand it.
> >
> > The TGCIA has reached agreement on which 4 of the 40 SRES baseline
> > scenarios would be most interesting (see meeting report: 4 scenarios
> (A1FI,
> > A2, B1 and B2) for 3 time periods 2020s, 2050s and 2080s). The next
> > question was: since a (maybe "the") core policy question is what the
> > benefits (or avoided impacts) would be of stabilizing GHG concentrations
> at
> > various levels, and since impact analysis should be based directly on GCM
> > results rather than on results from simple climate models/IA models, it
> > would be useful to also recommend a limited set of stabilization cases.
> To
> > make this a sensible effort, all the cases would have to be
> distinguishable
> > from one another from a GCM viewpoint. This may allow for combining
> various
> > scenarios which may be very different socio-economically, but would give
> > very similar climate results for this century, such as the B1 and 550,
> and
> > the 650 and B2 cases. The stabilization cases would be selected from the
> > following table, of which the cells contain available (post-SRES)
> scenario
> > runs:
> > |-------------+-------------+-------------+-------------+-------------|
> > | |450 ppm |550 ppm |650 ppm |750 ppm |
> > |-------------+-------------+-------------+-------------+-------------|
> > |A1T | | | | |
> > |-------------+-------------+-------------+-------------+-------------|
> > |A1B | | | | |
> > |-------------+-------------+-------------+-------------+-------------|
> > |A1FI | | | | |
> > |-------------+-------------+-------------+-------------+-------------|
> > |A2 | | | | |
> > |-------------+-------------+-------------+-------------+-------------|
> > |B1 | | | | |
> > |-------------+-------------+-------------+-------------+-------------|
> > |B2 | | | | |
> > |-------------+-------------+-------------+-------------+-------------|
> >
> > It was suggested to select 2-4 cases from the more than 70 scenarios runs
> > in the post-SRES programme co-ordinated by Tsuneyuki. Tom, it may well be
> > that your "post-WRE" work serves the same purpose, but the rationale for
> > selecting post-SRES cases would be: consistency with the SRES narratives
> > and numbers of the IPCC, and the much-acclaimed multi-model
> characteristics
> > of the (post-)SRES work. To downsize the 70-odd cases to 2-4 cases and
> not
> > burden Sarah too much, it was suggested to have one model (MAGICC) run a
> > subset of some 10-15 cases which seemed to make sense. Please also note
> > that not all 70-odd cases are useable, either because they do not have
> all
> > relevant GHG gases, or there have been questions about the
> > consistency/quality of their assumptions, e.g. a correct simulation of
> the
> > SRES base case by teams participating in post-SRES but not in SRES
> (right,
> > Tsuneyuki?). More importantly, Tsuneyuki used his intimate knowledge of
> all
> > cases and their distribution over base cases and stabilization levels to
> > recommend 13 cases. This selection was discussed with me and Naki during
> a
> > brief meeting in Washington in June and seemed to be a very appropriate
> > one.
> >
> > I noted the remark by Sarah that mean climate change results would be
> > rather be model-independent (for a given climate sensitivity), while
> > Tsuneyuki notes the large differences in the post-SRES work. These
> > differences may not have to do with different approaches with respect to
> > the carbon cycle or radiative forcing calculations, but rather with the
> > freedom modellers had (or rather: took) in selecting the time path
> (beyond
> > 2100) towards stabilization/time horizon, and the changes in emissions of
> > non-CO2 GHG in the stabilization analyses which focused primarily on CO2
> > stabilization. This would need to be clarified in detail for the runs to
> be
> > selected, and I suggest that only those runs are further used for which
> the
> > authors provide sufficient information on these issues.
> >
> > Concluding, I would like to ask Sarah, if she would be willing to take
> the
> > material provided by Tsuneyuki and perform the required calculations for
> > the 13 cases (radiative forcing, global mean temperature and sea level
> > rise, right, Mike/Tim?) within the next 1-2 months. The results would be
> > discussed electronically in a small group (the addressees of this
> message)
> > in October/November and a preliminary proposal based on these discussions
> > would be the input for a discussion on this issue during the next TGCIA
> > meeting in Barbados, in November. Tom's recent work may be useful for
> this
> > discussion as well, and I wonder if the mentioned (draft) papers could be
> > distributed to this group or even the full TGCIA.
> >
> > Kind regards,
> >
> > Rob
> >
> > Dr. Rob Swart
> > Head, Technical Support Unit
> > Intergovernmental Panel on Climate Change Working Group III: Mitigation
> > P.O. Box 1
> > 3720 BA Bilthoven
> > Netherlands
> > tel. 31-30-2743026
> > fax. 31-30-2744464
> > email: rob.swartatXYZxyzm.nl
>
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