Friday, March 30, 2012


date: Wed Nov 7 11:54:55 2007
from: Keith Briffa <>
subject: Re: Query on Arctic sea ice
to: Nathan Gillett <>

Hi Nathan
We used only the Hadley Centre model .We were looking at sea ice extent, in the expectation
that with more rapidly reducing circum North Atlantic tropospheric aerosol inputs (as
indicated by the latest estimates and the ice core concentrations) compared to the AR4
assumptions, we might expect more rapid local warming and faster ice melting than has
previously been expected. We note that HadCM3 had the lowest ice extent of all the models
anyway . We only looked at global mean temperature, which did not warm any faster with
reduced aerosol input than before. The sea ice extent was not significantly different from
the AR4 run. Thomas can show you these runs . He is still going to extract the spatial
pattern of warming from this run (right Thomas?) but other than that we pretty much
abandoned the idea of a quick paper indicating drastic immediate ice melt. The runs still
indicate no permanent sea ice with 30-50 years which is still amazing - but not
At 11:17 07/11/2007, you wrote:

Hi Keith,
This sounds interesting, and is new compared to other findings.. I was just at a
workshop on polar climate change and I think Marika Holland reported that none of the
IPCC models simulate single year decreases in summer minimum ice comparable to that
observed this year in the Arctic (some of the models such as the NCAR model do show
large interannual changes, but none as large as observed). Were you looking at changes
in summer minimum ice, or in annual mean ice? And how were these runs different from
e.g. the Hadley Centre's HadCM3 runs?
Keith Briffa wrote:

Dear all
this is best answered by Thomas Kleinen here , as he has just completed some runs
with the unified model and lower tropospheric aerosols than were previously input in the
recent 20th century - looking at the speed of sea ice melting and temperature change.
The bottom line is that the model gets roughly correct melting (close to what we
different than what we previously believed would happen".
At 09:14 05/11/2007, James Screen wrote:

I've been contacted by a Mr Mike Parr regarding the recent loss of Arctic
sea ice and it's implications on sea-ice/climate modeling. See email below.
I'm sure there is someone better placed than me to answer his query. Most of
my studies have focused on Antarctica and I don't consider myself a sea-ice
expert. If you think you can help Mr Parr please email him directly
-----Original Message-----
From: Mike Parr [[1]]
Sent: 04 November 2007 10:46
Subject: Arctic Ice loss
Dear Mr Screen,
I picked up your name from the CRU web site - forgive me for writing
direct but I have a question which you may not be able to answer
directly perhaps you know one of your colleagues that could.
I'm working with a couple of government agencies (European) on
climate change (isn't everybody these days). One of the issues I
would like to clear up is, given the recent and surprising loss of
arctic summer sea ice how current models may change.
If I look at Hadley centre data on this subject (which they seem to
obtain from CRU??) it seems somewhat out of kilter with what is
actually happening. I was wondering if (and how) models might be
modified in light of this year's developments? I would also be
interested in the link between arctic summer sea ice loss and if
anybody is giving some thought to how a changing arctic ocean albedo
might impact on ice outflows from Greenland (one could - not
unreasonably - imagine an acceleration in such outflows given an
albedo for sea ice of 0.6 to 0.8 and that for water of 0.05?).
Any help would be most appreciated,
best regards,
Mike Parr.

Professor Keith Briffa,
Climatic Research Unit
University of East Anglia
Norwich, NR4 7TJ, U.K.
Phone: +44-1603-593909
Fax: +44-1603-507784

Dr. Nathan Gillett,
Climatic Research Unit,
School of Environmental Sciences,
University of East Anglia,
Norwich NR4 7TJ, UK.
Tel: +44 (0) 1603 593 647
Fax: +44 (0) 1603 507 784

Professor Keith Briffa,
Climatic Research Unit
University of East Anglia
Norwich, NR4 7TJ, U.K.

Phone: +44-1603-593909
Fax: +44-1603-507784

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