cc: Tom Wigley <wigleyatXYZxyzr.edu>, "Thomas.R.Karl" <Thomas.R.KarlatXYZxyza.gov>, John.Lanzante@noaa.gov, carl mears <mearsatXYZxyzss.com>, "David C. Bader" <bader2atXYZxyzl.gov>, "'Francis W. Zwiers'" <francis.zwiersatXYZxyzgc.ca>, Frank Wentz <frank.wentzatXYZxyzss.com>, Karl Taylor <taylor13atXYZxyzl.gov>, Leopold Haimberger <leopold.haimbergeratXYZxyzvie.ac.at>, Melissa Free <Melissa.FreeatXYZxyza.gov>, "Michael C. MacCracken" <mmaccracatXYZxyzcast.net>, "'Philip D. Jones'" <p.jonesatXYZxyz.ac.uk>, firstname.lastname@example.org, Sherwood Steven <steven.sherwoodatXYZxyze.edu>, Steve Klein <klein21atXYZxyzl.gov>, "Thorne, Peter" <peter.thorneatXYZxyzoffice.gov.uk>, Tom Wigley <wigleyatXYZxyz.ucar.edu>, myles <m.allen1atXYZxyzsics.ox.ac.uk>
date: Mon, 31 Dec 2007 11:03:58 -0500
from: Dian Seidel <dian.seidelatXYZxyza.gov>
subject: Re: Douglass et al. paper
to: Susan Solomon <Susan.SolomonatXYZxyza.gov>
Dear Susan and Colleagues,
Thank you for sending this new article by Forster et al. and for
directing our attention to the role of the stratosphere on tropospheric
climate changes. I tend to agree with Susan's perspective on the
potential inability of AOGCMs to fully capture all 20th C climate
changes, some of which may be strongly coupled to ozone changes.
Tropical upper-tropospheric temperature changes, changes in tropopause
height, and changes in the "width" of the tropical belt (see attached),
may be among the changes more closely connected to ozone changes than to
other climate forcings and so might not be well simulated in current
In responding to Douglass et al., and in general, I hope we can leave
open the possibility that inadequately modeled stratospheric influences
may be among the explanations for discrepancies in temperature trend
profiles. Looking ahead to the next few years (why not, everyone else
does on December 31), we might anticipate (1) ozone levels to "recover"
and (2) a better understanding of the nature of stratospheric
temperature trends and their uncertainties (from the ongoing work of the
SPARC stratospheric temperature trends panel), which seem as significant
as tropospheric trend uncertainties. Both of these could affect actual
tropical upper tropospheric temperature trends and our estimation of
their magnitude. At some point, we will have a more holistic
stratospheric and tropospheric perspective on the trend profile
question, but until then we should be careful to acknowledge the
uncertainties stemming from the stratosphere.
Wishing you all a happy, healthy new year,
P.S. I've removed a few addresses of people I don't know from this
distribution, so if you "reply all", do so with care.
Susan Solomon wrote:
> Dear All,
> Thanks very much for the helpful discussion on these issues.
> I write to make a point that may not be well recognized regarding the
> character of the temperature trends in the lowermost
> stratosphere/upper troposphere. I have already discussed this with
> Ben but want to share with others since I believe it is relevant to
> this controversy at least at some altitudes. The question I want to
> raise is not related to the very important dialogue on how to handle
> the errors and the statistics, but rather how to think about the models.
> The attached paper by Forster et al. appeared recently in GRL. It
> taught me something I didn't realize, namely that ozone losses and
> accompanying temperature trends at higher altitudes can strongly
> affect lower altitudes, through the influence of downwelling longwave.
> There is now much evidence that ozone has decreased significantly in
> the tropics near 70 mbar. What we show in the attached paper by
> Forster et al is that ozone depletion near 70 mbar affects
> temperatures not only at that level, but also down to lower
> altitudes. I think this is bound to be important to the tropical
> temperature trends at least in the 100-50 mbar height range, possibly
> lower down as well, depending upon the degree to which there is a
> 'substratosphere' that is more radiatively influenced than the rest of
> the troposphere. Whether it can have an influence as low as 200 mbar -
> I don't know. But note that having an influence could mean reducing
> the warming there, not necessarily flipping it over to a net
> cooling. This 'long-distance' physics, whereby ozone depletion and
> associated cooling up high can affect the thermal structure lower
> down, is not a point I had understood despite many years of studying
> the problem so I thought it worthwhile to point it out to you here.
> It has often been said (I probably said it myself five years ago) that
> ozone losses and associated cooling can't happen or aren't important
> in this region - but that is wrong.
> Further, the fundamental point made in the paper of Thompson and
> Solomon a few years back remains worth noting, and is, I believe, now
> resolved in the more recent Forster et al paper: that the broad
> structure of the temperature trends, with quite large cooing in the
> lowermost stratosphere in the tropics, comparable to that seen at
> higher latitudes, is a feature NOT explained by e.g. CO2 cooling, but
> now can be explained by the observed ozone losses. Exactly how big
> the tropical cooling is, and exactly how low down it goes, remains
> open to quantitative question and improvement of radiosonde datasets.
> But I believe the fundamental point we made in 2005 remains true: the
> temperature trends in the lower stratosphere in the tropics are, even
> with corrections, quite comparable to that seen at other
> latitudes. We can now say it is surely linked to the
> now-well-observed trends in ozone there. The new paper further
> shows that you don't have to have ozone trends at 100 mbar to have a
> cooling there, due to down-welling longwave, possibly lower down
> still. Whether enhanced upwelling is a factor is a central question.
> No global general circulation model can possibly be expected to
> simulate this correctly unless it has interactive ozone, or prescribes
> an observed tropical ozone trend. The AR4 models did not include
> this, and any 'discrepancies' are not relevant at all to the issue of
> the fidelity of those models for global warming. So in closing let
> me just say that just how low down this effect goes needs more study,
> but that it does happen and is relevant to the key problem of tropical
> temperature trends is one that I hope this email has clarified.
> Happy new year,
> At 6:13 PM -0700 12/29/07, Tom Wigley wrote:
>> Yes -- I had this in an earlier version, but I did not want to
>> overwhelm people with the myriad errors in the D et al. paper.
>> I liked the attached item -- also in an earlier version.
>> Thomas.R.Karl wrote:
>>> This is a very nice set of slides clearly showing the problem with
>>> the Douglass et al paper. One other aspect of this issue that John
>>> L has mentioned and we discussed when we were doing SAP 1.1 relates
>>> to difference series. I am not sure whether Ben was calculating the
>>> significance of the difference series between sets of observations
>>> and model simulations (annually). This would help offset the
>>> effects of El-Nino and Volcanoes on the trends.
>>> Tom K.
>>> Tom Wigley said the following on 12/29/2007 1:05 PM:
>>>> Dear all,
>>>> I was recently at a meeting in Rome where Fred Singer was a
>>>> He was not on the speaker list, but, in advance of the meeting, I
>>>> had thought
>>>> he might raise the issue of the Douglass et al. paper. I therefore
>>>> prepared the
>>>> attached power point -- modified slightly since returning from
>>>> Rome. As it
>>>> happened, Singer did not raise the Douglass et al. issue, so I did
>>>> not use
>>>> the ppt. Still, it may be useful for members of this group so I am
>>>> sending it
>>>> to you all.
>>>> Please keep this in confidence. I do not want it to get back to
>>>> Singer or any
>>>> of the Douglass et al. co-authors -- at least not at this stage
>>>> while Ben is still
>>>> working on a paper to rebut the Douglass et al. claims.
>>>> On slide 6 I have attributed the die tossing argument to Carl Mears
>>>> -- but, in
>>>> looking back at my emails I can't find the original. If I've got
>>>> this attribution
>>>> wrong, please let me know.
>>>> Other comments are welcome. Mike MacCracken and Ben helped in putting
>>>> this together -- thanks to both.
>>> *Dr. Thomas R. Karl, L.H.D.*
>>> NOAA's National Climatic Data Center
>>> Veach-Baley Federal Building
>>> 151 Patton Avenue
>>> Asheville, NC 28801-5001
>>> Tel: (828) 271-4476
>>> Fax: (828) 271-4246
>>> Thomas.R.KarlatXYZxyza.gov <mailto:Thomas.R.Karl@noaa.gov>
>> Attachment converted: Junior:Comment on Douglass.ppt (SLD3/�IC�)
Dian J. Seidel
NOAA Air Resources Laboratory (R/ARL)
1315 East West Highway
Silver Spring, MD 20910
Phone: +1-301-713-0295 ext. 126
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