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cc: "''" <>
date: Fri, 23 Apr 1999 13:05:43 +0100
from: Merylyn McKenzie Hedger <>
subject: Fwd. re: US views on possible UK cooling- FYI
to: "''" <>, "''" <>, "''" <>, "''" <>

Dear Colleague,

This email arose from a discussion I first had with Granger Morgan who
has master-minded the US approach on socio-economic scenarios. When
shown the material on the UKCIP98 sceanrios his first reaction was what
about cooling, and Mike McCracken jumped in too. The US National
Assessment Synthesis team has gone for extremes on their economic and
demographic projections to capture all eventualities so I suppose
that's a different philosophy, reflected here.

By the way, most of the US National Assessment studies have used HADCM2,
(when I went to Washington last year they were only going with the
Canadian model, so Geoff did good work there). In some places, this has
produced results in sharp contrast to the Canadian model causing
problems. The NCAR model is just ready for use.

I hope to do the overall report on the meeting next week. I am telling
Mike McCracken I have forwarded his thoughts! My response when we spoke
was that currently UKCIP was focusing on getting awareness and action on
the changes which were likely in the 'near' term.

>From Mike McCracken


Dear Merylyn--To follow-up on our discussion with Granger in Atlanta, I
went and looked at the plots I have. Both Granger and I would interpret
this as iimplying that there is indeed a chance of a cooling scenario
the UK, even if not a full crash of the Atlantic circulation.

Thanks again for coming to Atlanta, Mike

>Date: Wed, 21 Apr 1999 13:43:20 -0400
>To: gmorgan
>From: Mike MacCracken <>
>Subject: North Atlantic overturning
>Dear Granger--Following up on our discussion in Atlanta with Merylyn
>McKenzie Hedger and the risk of cooling in the UK and Europe, I went
>and checked the figures for predictions for the North Atlantic
>changes from the GCDL and Hadley models:
>1. GFDL:
>Control--20 Sverdrups
>up to 2 times CO2 at 1% per year and stabilize--drops to about 7 and
>recovers over long time
>up to 4 times CO2 at 1% per year and stabilize--drops to about 2 and
>2. Hadley Centre model
>control--about 22-23 Sverdrups
>IPCC BAU-drops to about 17
>up to 4 times CO2 at 2% per year--drops to about 14 and slwoly goes up
>about 16
>The dates on the Hadley figure are a bit strange--their BAU case starts
>dropping in about 1980-90. Their up to 4 times CO2 drops in about 1890
>(yes, 110 years ago), so I assume they started their run in about 1860
>started the sharp CO2 increase then.
>Thus, with respect to Merylyn's comments about the UK model not showing
>collapse, true, but. Basically, the GFDL run does show a stronger
>reduction, but the Hadley model does also show a significant decrease
>well. I think I might worry about a potential cooling.

Michael C. MacCracken, Ph.D.
National Assessment Coordination Office
Suite 750
400 Virginia Avenue
Washington DC 20024

Tel: (202) 314-2230 (Main number for NACO and for Robert Cherry, Admin.
Tel: (202) 314-2233 (office and voicemail)
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