date: Tue Mar 24 10:59:17 2009
from: Tim Osborn <t.osborn@uea.ac.uk>
subject: Re: Northern Latitude differences
to: Deborah Hemming <debbie.hemming@metoffice.gov.uk>

   Hi Debbie,
   I took at look at the 1951-2000 Jan pattern -- as you say, it is still amplified at the
   poles compared to our CMIP3 HadCM3 pattern.  Chris suggested this could be due to a genuine
   difference in model versions.  Have you got the other 11 months for the longer 1951-2000
   period yet?  I'll take a look at them if you have.
   Cheers
   Tim
   At 19:40 06/03/2009, you wrote:

     Tim,
       Sorry I havnt been able to finish the patterns, attached is the
     January pattern for the standard run 1951-2100 30 year running mean, it
     is improved but still too amplified in the poles.
       Unfortunately, I am away now for 2 weeks so will have to sort this out
     when i'm back. Sorry again for the delay.
     Cheers,
     Debbie.
     On Wed, 2009-03-04 at 14:27 +0000, Tim Osborn wrote:
     > Thanks for that Debbie.  Please note that I did *not* used 1900-2100
     > for the regressions.  We used 1951-2099 or 1951-2100 depending on
     > which year the runs finished in.  Feel free to also do 1900-2099/2100
     > to investigate sensitivity to this further, if you want, but with
     > 1951-2099 you've already replicated our analysis period so you could
     > just send those new patterns if you like.
     >
     > re. sensitivity.  yes, the 20th century has lower slope in the local
     > changes, but also lower slope in the global-mean temperature that is
     > being regressed against.  So, you wouldn't definitely get a
     > sensitivity to period of analysis.  However in sea-ice areas this
     > might be more non-linear and hence the biggest local changes might
     > only occur after some degree of global warming, which could lead to
     > the effect that you describe.  This also invalidates the
     > pattern-scaling concept, but for surface air temperature I only
     > pattern-scale over land, so the Arctic sea-ice area isn't much of a
     > concern.  Of more concern are the N. American differences in Jan-May,
     > which are over land.  It would be nice to see if your new 1951-2099
     > patterns match mine better in this region.
     >
     > Cheers
     >
     > Tim
     >
     > At 14:19 04/03/2009, Deborah Hemming wrote:
     > >It seems that the difference may be because of the different time period
     > >over which the regression was performed.  I've just compared my previous
     > >output (2000-2099 period 30 year running mean) with the same but for the
     > >period 1951-2099, which is closer to the 1900-2100 period Tim uses.
     > >This second pattern is ~2C lower (more comparable with Tim's) in the
     > >polar regions than the first.
     > >
     > >This completely makes sense to me because the lower slope of the
     > >relationship during the 20th century is forcing the regression slope to
     > >be lower...esp in the high change regions.  However, I really hadn't
     > >expected it to be so sensitive, which is somewhat disturbing!  I want to
     > >check a couple more ideas and extend the time to cover the whole
     > >1900-2100 period, which i'll probably have to do overnight, but should
     > >be able to send some more reasonable QUMP patterns, at least for average
     > >temperature, to Tim tomorrow.
     > >
     > >Sorry this is taking so long to sort out, but it's very useful for me at
     > >least to appreciate the scale of differences that subtle variations in
     > >the methods used for pattern scaling can make.  I think this also
     > >justifies us being very careful to use the same method for all data in
     > >QUEST-GSI.
     > >
     > >Cheers,
     > >Debbie.
     > >
     > >On Wed, 2009-03-04 at 13:38 +0000, Tim Osborn wrote:
     > > > something like Chris' suggestion below seems more likely than a bug
     > > > in your code, Debbie.  A bug would more likely either make the
     > > > results unrecognisable or, if more minor, affect results more widely
     > > > rather than having a high-latitude focus.
     > > >
     > > > Tim
     > > >
     > > > At 19:23 03/03/2009, Chris Huntingford wrote:
     > > > >Dear Debbie (cc Ben Booth)
     > > > >
     > > > >I can cover on Thursday.
     > > > >
     > > > >I was thinking about the GCM differences. There were a couple of
     > > > >small bugs that we found in HadCM3 land surface description that we
     > > > >didn't think made much difference when tested back in a full GCM
     > > > >simulation. Martin Best knows what the problems are, but I do have
     > > > >the vague memory of somebody saying they are most likely to make the
     > > > >largest differences in Northern Latitudes, mainly due to snow
     > > > >interactions. The "correct" simulation, hopefully bug-free, was made
     > > > >by Spencer Liddicoat, and the patterns are those that I sent you.
     > > > >Job number "afsyb".
     > > > >
     > > > >When we fitted the patterns to the QUMP runs, I cannot remember
     > > > >whether Ben Booth made patterns for the standard run too - I'm happy
     > > > >to make an intercomparison. Ben, do you have IMOGEN patterns for the
     > > > >control i.e. for each month - I'm struggling to remember?. Failing
     > > > >that, I could look at the very old patterns we used in the original
     > > > >HadCM3 simulation i.e. by Peter and I back in year 2000.
     > > > >
     > > > >I'm in CEH tomorrow morning after 10am if you want to ring. It's
     > > > >quite likely that you have not made an error, but in fact finding
     > > > >differences due to physics enhancement.
     > > > >
     > > > >All the best,
     > > > >Chris.
     > > > >
     > > > >
     > > > >
     > > > >
     > > > >
     > > > >Chris Huntingford
     > > > >Climate Change Modeller
     > > > >+44 (0)1491 692389
     > > > >+44 (0)7884437138
     > > > >Centre for Ecology and Hydrology, Benson Lane, Wallingford, OX10 8BB, U.K.
     > > > >[1]http://www.ceh.ac.uk/staffWebPages/DrChrisHuntingford.html
     > > > >
     > > > > >>> Deborah Hemming <debbie.hemming@metoffice.gov.uk>
     > > 03/03/2009 18:23 >>>
     > > > >Nigel,
     > > > >
     > > > >   I'm currently checking with Tim and Chris to ensure that the patterns
     > > > >i'm producing with QUMP (using the ClimGen approach) are reasonable
     > > > >compared to those Tim has done already.
     > > > >
     > > > >   Tim has made a comparison of the temperature patterns generated from
     > > > >the Standard run (HadCM3) from his code for ClimGen and mine using the
     > > > >QUMP standard run (basically similar to HadCM3 standard).  We are
     > > > >concerned that my pattern was ~2C amplified in the N Polar region
     > > > >compared to Tim's ClimGen.  Currently i'm running tests to diagnose
     > > > >where the problem/error may be and should have some answers on this over
     > > > >the next 2 days.
     > > > >
     > > > >   I am very pushed for time and will be away for the following 2 weeks,
     > > > >so think it will be more worthwhile if I spend Thursday trying to sort
     > > > >this out rather than attend the meeting.  Hope that doesnt cause any
     > > > >problems.  I will update you on the latest at end of day tomorrow.
     > > > >
     > > > >Cheers,
     > > > >Debbie.
     > > > >
     > > > >On Tue, 2009-03-03 at 14:37 +0000, Nigel Arnell wrote:
     > > > > > Debbie / Tim,
     > > > > >
     > > > > > Will you be able to update us on the status of the QUMP/ClimGen
     > > > > > scenarios on Thursday?
     > > > > >
     > > > > > Thanks
     > > > > >
     > > > > > Nigel
     > > > > >
     > > > > >
     > > > > > Professor Nigel Arnell
     > > > > > Director
     > > > > > Walker Institute for Climate System Research
     > > > > > University of Reading
     > > > > > Earley Gate
     > > > > > RG6 6BB
     > > > > > UK
     > > > > >
     > > > > > +44-118-378-7392
     > > > > > [2]www.walker-institute.ac.uk
     > > > > >
     > > > > >
     > > > > >
     > > > >--
     > > > >Dr Deborah Hemming (Manager, Climate Impacts Analysis)
     > > > >Met Office Hadley Centre for Climate Change
     > > > >Fitzroy Road   Exeter   Devon   EX1 3PB
     > > > >tel: +44 (0)1392 885715  fax: +44 (0)1392 885681
     > > > >web: [3]http://www.hadleycentre.co.uk
     > > > >
     > > > >
     > > > >--
     > > > >This message (and any attachments) is for the recipient only. NERC
     > > > >is subject to the Freedom of Information Act 2000 and the contents
     > > > >of this email and any reply you make may be disclosed by NERC unless
     > > > >it is exempt from release under the Act. Any material supplied to
     > > > >NERC may be stored in an electronic records management system.
     > > >
     > > > Dr Timothy J Osborn, Academic Fellow
     > > > 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:      [4]http://www.cru.uea.ac.uk/~timo/
     > > > sunclock: [5]http://www.cru.uea.ac.uk/~timo/sunclock.htm
     > > >
     > > >
     > >--
     > >Dr Deborah Hemming (Manager, Climate Impacts Analysis)
     > >Met Office Hadley Centre for Climate Change
     > >Fitzroy Road   Exeter   Devon   EX1 3PB
     > >tel: +44 (0)1392 885715  fax: +44 (0)1392 885681
     > >web: [6]http://www.hadleycentre.co.uk
     >
     > Dr Timothy J Osborn, Academic Fellow
     > 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:      [7]http://www.cru.uea.ac.uk/~timo/
     > sunclock: [8]http://www.cru.uea.ac.uk/~timo/sunclock.htm
     >
     >
     --
     Dr Deborah Hemming (Manager, Climate Impacts Analysis)
     Met Office Hadley Centre for Climate Change
     Fitzroy Road   Exeter   Devon   EX1 3PB
     tel: +44 (0)1392 885715  fax: +44 (0)1392 885681
     web: [9]http://www.hadleycentre.co.uk

