Tuesday, March 27, 2012

2885.txt

cc: P.Jones@uea.ac.uk, Brian Hoskins <b.j.hoskinsatXYZxyzding.ac.uk>, Susan Solomon <susan.solomonatXYZxyza.gov>, martin.manning@noaa.gov, Matilde Rusticucci <matiatXYZxyzfcen.uba.ar>, Peter Lemke <plemkeatXYZxyz-bremerhaven.de>, Jurgen Willebrand <jwillebrandatXYZxyz-geomar.de>, Nathan Bindoff <n.bindoff@utas.edu.au>, zhenlin chen <cdcccatXYZxyz.gov.cn>, Melinda Marquis <marquisatXYZxyzr.edu>
date: Wed, 10 Jan 2007 11:42:04 -0700
from: Kevin Trenberth <trenbertatXYZxyzr.edu>
subject: Re: IPCC WG1 Observations Conference Call
to: Susan Solomon <ssolomonatXYZxyznoaa.gov>

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Hi all
A key question here is to what extent are we limited to working with
blinkers on and confining our statements to observations alone? This
relates to understanding, some of which has been developed through
modeling and consistency. It is not physically possible to have a
change in the westerlies without affecting storm tracks also. Indeed
the analyses are not as unequivocal on the issues of changes in
intensity and frequency, but our understanding and model results support
the interpretation of increases in intensity (e.g. through increased
moisture there is increased latent heating) and a change in frequency
and duration. This is what is suggested by models and so maybe it
belongs more in chapter 9 related stuff, but I have to admit to some
frustration about observationalists not being allowed to use physical
reasoning. In the real world we have only one member of the "ensemble"
and we can not beat down the random noise.

With that off my chest, see below.

Susan Solomon wrote:
> Dear All,
>
> Thanks very much for the helpful discussion, which I think is inching
> to closure.
>
> May I suggest that we not drop the 'in both hemispheres' language,
> whatever else is done.
>
> With this change, there seem to me to be three options that have
> emerged from the suggestions, with diffeent issues associated with each:
>
> 1) Mid-latitude westerly winds in both hemispheres have shifted
> polewards and strengthened since the 1960s, with associated changes in
> storms. (3.5)
>
> Problem: this is too vague. Do we mean moving or strengthening?
> both? is this misleading if although storms may have strengthened
> they may also be fewer in number?
We mean both, and I don't think it is too vague. It is deliberately
vague on storms but it would be misleading to assume storms are
unchanged and so I don't think it should be left out.
>
> Also: the assessment of chapter 3 seems to be quite uncertain on the
> issue of the confidence in the strengthening and whether the numbers
> of storms have changed significantly, so perhaps it is not appropriate
> to highlight in the SPM. It seems to me that from chapters 3 we
> can be reasonably clear on the issue of the poleward shift. That is
> highly policy-relevant. It also links with chapter 9's attribution
> statement later on a related issue.
Agree with this commentary.
> So option 2 could be:
>
> 2) Mid-latitude westerly winds in both hemispheres have shifted
> polewards and strengthened since the 1960s. Storms have shifted
> polewards in association with this change. (3.5)
Prefer the first.
>
> Finally, if we are not comfortable at all with any statement about
> storms, we can stop with the first sentence, as Phil suggests:
>
> 3) Mid-latitude westerly winds in both hemispheres have shifted
> polewards and strengthened since the 1960s. (3.5)
As I say above, this would be an error of omission as the storms can not
stay unchanged.
Hope this helps
Kevin
>
> Please give me your thoughts.
> bests,
> Susan
>
>
>
> t 5:25 PM +0000 1/10/07, P.JonesatXYZxyz.ac.uk wrote:
>> Dear All,
>> Agree with Brian's new bullet. I still think we will
>> get comments about what changes with storms. If this
>> is going to lead somewhere we don't want it and cause
>> problems, then the final part is likely best removed.
>>
>> Reading it again, better if we say .. since the 1960s.
>> About is a little vague.
>>
>> Back in CRU on Friday. I may be able to get this hotel link
>> to work tomorrow morning.
>>
>> Cheers
>> Phil
>>
>>
>>> Dear All
>>>
>>> To me a headline should be kept simple with the detail in the bullets
>>> below, so I prefer the simple version with "aspects of extreme
>>> weather"
>>> but I guess I am outvoted on that!
>>>
>>> For the first part of the bullet on the westerlies I should prefer to
>>> revert to including the shift and also using the word strengthen
>>> rather
>>> than increase (a number, such as the speed, increases):
>>>
>>> Mid-latitude westerly winds have shifted polewards and stengthened
>>> since
>>> about the 1960s.
>>>
>>> The next part on the storms is problematic. I agree with Kevin that we
>>> should steer clear of the causal langauage Susan had used. However
>>> Kevin's words seemed to link a shift in the storm tracks with an
>>> increase in the winds. Also, as reviewed in 3.5.3, some papers suggest
>>> that, in addition to a poleward shift in the storm tracks and an
>>> increase in their average intensity, there is a decrease in the number
>>> of storms . This is probably too much for the bullet, so that a less
>>> specific version may be required.
>>>
>>> I think the whole bullet could be:
>>>
>>> Mid-latitude westerly winds have shifted polewards and stengthened
>>> since
>>> about the 1960s, with associated changes in storms. (3.5)
>>>
>>> Brian
>>>
>>>
>>> Susan Solomon wrote:
>>>
>>>> Thanks Brian and Kevin for the help.
>>>>
>>>> I agree with Brian about reversing the order in the headline sentence
>>>> but agree with Kevin that a separate bullet is most helpful. I
>> >> suggest we keep the headline short and simple and just leave the
>>>> language we have about wind patterns being one of several things
>>>> changing there. Otherwise it could be read as putting the
>>>> circulation
>>>> change into a very high prominence in the headline which isn't quite
>>>> the emphasis we were discussing, I think.
>>>>
>>>> I tried to combine the suggestions and to keep things clear enough
>>>> that governments won't complain about lack of specifics. If you
>>>> look
>>>> over the comments, you will have seen that above all they will not
>>>> tolerate vague language. Anybody who was in Shanghai (or any other
>>>> IPCC meeting) can attest to that so please please everybody help make
>>>> things as specific as we can.
>>>>
>>>> So my suggestion for the wind pattern bullet is:
>>>>
>>>> Mid-latitude westerly wind speeds have increased in both hemispheres
>>>> since about the 1960s. This has caused storm tracks to move towards
>>>> higher latitudes. {3.6}
>>>>
>>>> Regarding the headline that proceeds it, can we consider something
>>>> like this:
>>>>
>>>> At continental or ocean basin scales, numerous changes in climate
>>>> have
>>>> been observed. These include sea ice extent, precipitation amounts,
>>>> ocean salinity, wind patterns, and [aspects of extreme weather] OR
>>>> [the frequency of heavy precipitation and of heat waves, the
>>>> intensity
>>>> and duration of drought, and the intensity of hurricanes and
>>>> typhoons.]
>>>>
>>>> The ice sheets have been taken out of the above because they are
>>>> moving to a consolidated sea level subsection, to deal with several
>>>> requests for that.
>>>>
>>>> Is the new option after wind patterns too specific? I am a little
>>>> concerned that we will be challenged on that. We could keep what we
>>>> have: 'aspects of extreme weather'. Equally, I am worried that they
>>>> will challenge the vagueness of 'extreme weather' so that is why you
>>>> see two alternatives here.
>>>>
>>>> Thoughts?
>>>> Susan
>>>>
>>>>
>>>> At 8:54 AM -0700 1/9/07, Kevin Trenberth wrote:
>>>>
>>>>> Hi Brian
>>>>> Do you need the first part? Are you rewriting the headline on SPM p
>>>>> 5 lines 35-37 or are you adding an extra bullet on circulation?
>>>>> I thought we agreed on the latter, but your piece seems more like
>>>>> the
>>>>> former.
>>>>>
>>>>> If we left the headline alone and added:
>>>>
>>>>> * Changes in large-scale atmospheric circulation are apparent
>>>>> and, in particular, the mid-latitude westerly winds have
>>>>> shifted polewards and strengthened, altering storm tracks.
>>>>>
>>>>> would be an alternative approach. I think it is helpful to mention
>>>>> storm tracks but not be specific about how they have changed.
>>>>> What do you think?
>>>>> Kevin
>>>>>
>>>>> Brian Hoskins wrote:
>>>>>
>>>>>> Susan
>>>>>>
>>>>>> Headline 2
>>>>>>
>>>>>> I suggest the following:
>>>>>>
>>>>>> At continental or ocean basin scale, numerous changes in climate
>>>>>> have been observed. Mid-latitude westerly winds (and the associated
>>>>>> storms) have shifted polewards and strengthened. Other climate
>>>>>> changes include precipitation,.....
>>>>>>
>>>>>> I have taken the suggestion form SPM_327 to reverse the order of
>>>>>> the
>>>>>> first sentence.
>>>>>>
>>>>>> The westerly winds sentence is essentially that in a headline in
>>>>>> the
>>>>>> TS.
>>>>>>
>>>>>> I should much prefer not to include the bracketed itallicised
>>>>>> phrase
>>>>>> on storms. The evidence is less strong. There is some evidence for
>>>>>> reduced numbers of storms also but no room to say that. It was not
>>>>>> headlined in the chapter or the TS.
>>>>>>
>>>>>> Best wishes
>>>>>>
>>>>>> Brian
>>>>>
>>>>>
>>>>> --
>>>>> ****************
>>>>> Kevin E. Trenberth e-mail: trenbertatXYZxyzr.edu
>>>>> <mailto:trenbert@ucar.edu>
>>>>> Climate Analysis Section,
>>>>> www.cgd.ucar.edu/cas/trenbert.html
>>>>> <http://www.cgd.ucar.edu/cas/trenbert.html>
>>>>> NCAR
>>>>> P. O. Box 3000, (303) 497 1318
>>>>
>>>>> Boulder, CO 80307 (303) 497 1333 (fax)
>>>>>
>>>>> Street address: 1850 Table Mesa Drive, Boulder, CO 80305
>>>>
>>>>
>>>
>>>

--
****************
Kevin E. Trenberth e-mail: trenbertatXYZxyzr.edu
Climate Analysis Section, www.cgd.ucar.edu/cas/trenbert.html
NCAR
P. O. Box 3000, (303) 497 1318
Boulder, CO 80307 (303) 497 1333 (fax)

Street address: 1850 Table Mesa Drive, Boulder, CO 80305

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