cc: plattner@climate.unibe.ch, Jonathan Overpeck <jto@u.arizona.edu>, Stefan Rahmstorf <rahmstorf@ozean-klima.de>, Anders Levermann <levermann@pik-potsdam.de>, Eva Bauer <eva.bauer@pik-potsdam.de>, Eystein Jansen <eystein.jansen@geo.uib.no>, t.osborn@uea.ac.uk, joos <joos@climate.unibe.ch>
date: Tue, 21 Feb 2006 09:20:37 -0700
from: Jonathan Overpeck <jto@u.arizona.edu>
subject: Re: Fwd: Re: Millennium Simulations
to: Keith Briffa <k.briffa@uea.ac.uk>

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Many thanks.

>now working on stitching all bits together (thanks Fortunat for your 
>text) - and , (other than final refs which are a mess!) the 2000 
>year section should come by tomorrow evening my time - still having 
>to juggle University and teaching/committee crap) . Keith
>
>
>At 16:33 20/02/2006, Tim Osborn wrote:
>>Dear all,
>>
>>after talking with Keith about the exact wording to use in the text 
>>to describe how the stronger solar forcing assumption raises the 
>>variability of the simulated temperatures, I've realized that it 
>>might be misleading to say that the standard deviation of natural 
>>variability of NH temperature is 58-72% higher if the strong solar 
>>forcing is assumed than if the weak solar forcing is assumed.  The 
>>reason is that these figures refer only to the natural variability 
>>that is *forced* (unless these models have internally-generated 
>>variability -- inspection of the control runs for Bern2.5CC and 
>>Climber2 suggests that they don't).  If internally-generated 
>>variability had a standard deviation (for 30-year smoothed NH 
>>temperatures) of, say, 0.08 K (from HadCM3), then the stronger 
>>solar case would have total natural variability only 28-40% greater 
>>than the weaker solar case.
>>
>>Is this right?  If so, should we just change the text to indicate 
>>that we only mean natural variability due to external forcings?
>>
>>Cheers
>>
>>Tim
>>
>>At 15:23 20/02/2006, Fortunat Joos wrote:
>>>Thanks Tim. This sounds good.
>>>
>>>Tim Osborn wrote:
>>>>At 15:23 15/02/2006, Fortunat Joos wrote:
>>>>
>>>>>TIM can you please give us the appropriate number for the 
>>>>>low-freq. NH T variability and specify the smoothin.
>>>>
>>>>Hi Fortunat,
>>>>for the smoothing actually used on the Climber2/3a/Bern2.5CC 
>>>>figure (30-year smoothing), these are the standard deviations of 
>>>>the simulated NH temperatures for the "only natural forcings 
>>>>runs":
>>>>         Bard08-WLS   Bard25   Ratio of standard deviations
>>>>Bern    0.103        0.177    1.72
>>>>Clm2    0.078        0.123    1.58
>>>>Clm3a   0.092        0.147    1.60
>>>>So, the multi-decadal variability in NH surface air temperature 
>>>>is between 58% and 72% greater under the stronger solar forcing 
>>>>(Bard25) than under the weaker solar forcing (Bard08-WLS).
>>>>This can go in the text where Fortunat indicated.  OK everyone?
>>>>Cheers
>>>>Tim
>>>>
>>>>Dr Timothy J Osborn
>>>>Climatic Research Unit
>>>>School of Environmental Sciences, University of East Anglia
>>>>Norwich  NR4 7TJ, UK
>>>>e-mail:   t.osborn@uea.ac.uk
>>>>phone:    +44 1603 592089
>>>>fax:      +44 1603 507784
>>>>web:      http://www.cru.uea.ac.uk/~timo/
>>>>sunclock: http://www.cru.uea.ac.uk/~timo/sunclock.htm
>>>
>>>--
>>>
>>>   Climate and Environmental Physics,
>>>   Physics Institute, University of Bern
>>>   Sidlerstr. 5, CH-3012 Bern
>>>   Phone:    ++41(0)31 631 44 61      Fax:      ++41(0)31 631 87 42
>>>   Internet: http://www.climate.unibe.ch/~joos/
>>
>>Dr Timothy J Osborn
>>Climatic Research Unit
>>School of Environmental Sciences, University of East Anglia
>>Norwich  NR4 7TJ, UK
>>
>>e-mail:   t.osborn@uea.ac.uk
>>phone:    +44 1603 592089
>>fax:      +44 1603 507784
>>web:      http://www.cru.uea.ac.uk/~timo/
>>sunclock: http://www.cru.uea.ac.uk/~timo/sunclock.htm
>
>--
>Professor Keith Briffa,
>Climatic Research Unit
>University of East Anglia
>Norwich, NR4 7TJ, U.K.
>
>Phone: +44-1603-593909
>Fax: +44-1603-507784
>
>http://www.cru.uea.ac.uk/cru/people/briffa/


-- 
Jonathan T. Overpeck
Director, Institute for the Study of Planet Earth
Professor, Department of Geosciences
Professor, Department of Atmospheric Sciences

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