Monday, June 11, 2012


cc: Susan Solomon <>, "Thomas.R.Karl" <>, <>, "David C. Bader" <>, "'Dian J. Seidel'" <>, "'Francis W. Zwiers'" <>, Frank Wentz <>, Karl Taylor <>, Leopold Haimberger <>, Melissa Free <>, "'Philip D. Jones'" <>, <>, Sherwood Steven <>, Steve Klein <>, "Thorne, Peter" <>, Tim Osborn <>, Tom Wigley <>, myles <>, Bill Fulkerson <>
date: Tue, 01 Jan 2008 11:22:39 -0500
from: Mike MacCracken <>
subject: Re: Douglass et al. paper
to: Tom Wigley <>, carl mears <>

Hi Tom--I would also think that, in relating the temperature rise to Cl-Cl
relationship, it important to recognize that most of the evaporation that
becomes rainfall is from warmer parts of world where the delta-T is smaller
than global average, whereas much of the delta-T is from the more polar
regions that are colder and where little of evaporation for rainfall comes
from. So, looking for a percentage change based on average temperature
change is not a valid presumption.

It is also interesting that, in the model runs which Ken Caldeira has done
to test the idea I had 5 years or so ago of geoengineering just in the
Arctic (that is, reducing solar only over the Arctic) in order not to impose
large reduction in solar direct over most of the world and to take advantage
of albedo feedback effect, the temperature in the Arctic and adjoining
midlatitude regions drops, but the precipitation in the Arctic does not drop
much at all--mainly, we suspect because the loading of atmospheric water
vapor is controlled in the lower latitudes where the Arctic dimming has
little effect on temperature. Indeed, in the Arctic the precipitation is now
snow instead of rain (as in the CO2 doubling case), but the amount does not
go down--and, indeed, having more snow would help to build back glaciers and
Greenland Ice Sheet and help to reduce sea level rise. So, sort of a double

Best, Mike M

On 1/1/08 10:58 AM, "Tom Wigley" <> wrote:

> Carl,
> A long time ago I wondered why global-mean precip change in GCMs per
> degree global-mean warming was less than Cl-Cl (as in many diagrams from
> IPCC 1990 onwards). My answer comes from partially differentiating the
> surface energy budget equation at constant RH. This, from memory, is a
> little tricky -- I've got my sums somewhere that I'd need to hunt for.
> Anyhow,
> d(precip)/d(T) comes to about 3% per degree C.
> Tom.
> (For 'd', read backwards 6. Can't seem to get to this with Thunderbird.)
> +++++++++++++++++++++++++++++
> carl mears wrote:
>> Hi Susan and others...
>> Thanks for pointing out the Forster et al paper. I've been wondering
>> about the effect of ozone on the
>> tropical upper tropospheric temperature trends since I saw the
>> vertical trends profile from
>> "GFDL CM 2.1x" at the SPARC temperature trends meeting last spring.
>> My question: is this effect big enough to affect precipitation
>> trends. If so it could help
>> explain the discrepancy between our SSM/I precipitation trends and the
>> sub-clausius-clapeyron
>> trends predicted under CO2 increase. (Wentz et al 2007, Held and
>> Soden, Allen et al).
>> Steve Sherwood and I emailed about this a few months ago, and at the
>> time, we concluded "no",
>> based on a simple model. Do these new results change this conclusion?
>> -Carl
>> At 09:18 AM 12/30/2007, 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,
>>> Susan
>>> At 6:13 PM -0700 12/29/07, Tom Wigley wrote:
>>>> Tom,
>>>> 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.
>>>> Tom.
>>>> +++++++++++++
>>>> Thomas.R.Karl wrote:
>>>>> Tom,
>>>>> 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
>>>>>> participant.
>>>>>> 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.
>>>>>> Tom.
>>>>>> ++++++++++++++++++++++++++++++++++++++++
>>>>> --
>>>>> *Dr. Thomas R. Karl, L.H.D.*
>>>>> */Director/*//
>>>>> 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
>>>>> <>
>>>> Attachment converted: Junior:Comment on Douglass.ppt (SLD3/�IC�)
>>>> (0022CEF5)
>> Dr. Carl Mears
>> Remote Sensing Systems
>> 438 First Street, Suite 200, Santa Rosa, CA 95401
>> 707-545-2904 x21
>> 707-545-2906 (fax))

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