Monday, May 7, 2012


date: Tue, 25 Feb 1997 18:14:42 +0000 (GMT)
from: J Mitchell <>
subject: Re: IPCC scenario team
to: (Mike Hulme)

> John,
> I have had an approach from IIASA (Nakicenovic and Gruebler) to join the
> writing team for the new IPCC emissions scenarios for the 2000 IPCC
> assessment (see email below). They seem to want someone who has a grasp of
> what GCM'ers, and simple modellers, might need/use with regard to designing
> different forcings for climate change simulations. While I have some idea
> about how we have used such scenarios in Tom's model (MAGICC), I only have a
> sketchy idea about what your sort of requirements might be (especially in
> regard to sulphur)
Hi Mike
I have a responsibility in CLIVAR to guide forcing scenarios - CLIVAR is
more interested in science but I think recognises that it must be seen to
cooperate with IPCC. I think the best way is for modellers to use simple
scenarios which bracket the range of interest, but there is political
pressure to do actual scenarios. Big centres may do both. I don't want to
get involved in any more committees, but i will help where I have time

> I would be prepared to accept the invitation but only if I was sure I could
> adequately represent the sort of viewpoint on these questions which GCM'ers
> may have. What would your advice be? Does this require someone else to do
> the job properly (if so is there anyone in Hadley who could be appropriated)
> or are your concerns fairly general and therefore ones that I could
> adequately represent in the report/writing process? I don't want to end up
> trying to (mis?)represent views which some climate modellers may hold very
> strongly.
> The sort of questions I imagine to be important are:
> 1) are GCM-based simulations going to make use of detailed scenario data, or
> more likely use generalised appoximations such as 0.5% or 1% p.a. CO2
> equivalent?
Hard to answer. Off the top of my head, I would prefer simple scenarios
as you sugggest for scientific purposes and one or so stabilization
scenarios. In practice, I think we and places like Hamburg might run some
"real" scenarios
> 2) what priorities are GCM'ers likely to have in the future: middle of the
> road scenarios, high scenarios, low scenarios or stabilisation scenarios?
Ideally, as few as we can cover the range with.
> 3) what range of gas species would a GCM forcing scenario potentially use
> (now and in 3 years time)?
For example, we can cope with CO2 O3 N2O CH4 CFC11,12.
> 4) what spatial disaggregation is necessary (for S and for GHGs)?
Emissions or concentrations?
> Some of these questions were mentioned in the IPCC Climate Scenario
> Taskgroup and some are pertinent to the use of scaling methods etc.
> Thanks for your advice on this one.
> Mike
> ____________________________________________________________________
> Mike
> I write to you to find out your interest in participating in the
> writing team for the development of a new set of IPCC emissions
> scenarios (convening lead author: N. Nakicenovic from IIASA).
> I feel it would be very important to involve you as representative
> of the climate modelers, i.e. an important user community of such
> scenarios. Unfortunately, the time frame of the work suggested by
> Bob and Eric is near infeasible: they want the special report go to
> expert review by mid-1998, which leaves about one year for the
> development of scenarios. Please let me know if you see any chance
> at all for participating actively in this important activity.
> As a kind of example of the inputs expected from you let me address
> another small request.
> I have been asked to draft a short (3 page) discussion paper on
> sulfur emissions and their role in the new round of scenarios.
> I would be interested to get your advice what would be an:
> 1. ideal set of sulfur emissions
> and
> 2. an absolute minimum set of sulfur emissions
> you would expect from emission scenarios that are useful inputs to
> simple and (lateron) also complex climate models (e.g. time periods,
> spatial resolution, disaggregation by source, range of emissions
> etc.).
> I have a good grasp what is possible in terms of energy sector
> models. However, considering that sulfur is only one (although
> important) gas species, it is important to define the requirements
> on the scenarios not in terms what would be possible under ideal
> conditions (i.e. ample of time and money), but rather what is the
> minimum output requirements for the scenarios still to be useful.
> Obviously, in light of recent findings what the new scenarios should
> consider more explicitly are more vigorous sulfur control scenarios.
> Suggestions are most welcome.
> Reference to the IS92 series would also be helful for this assessment as
> well.
> Many thanks in advance for your help. I hope it will be possible for
> you to come on board this effort!
> Bets regards, Arnulf.

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