Saturday, April 28, 2012


date: Fri, 12 Jan 2007 16:09:27 +0000
from: Phil Jones <>
subject: Re: PDSI
to: Gerard van der Schrier <>


Not sure what you mean? What IPCC Obs? OK Keith
tells me it's the chapter. Here's the text file. Figures come
in 3 parts. Don't pass the text on. Tell me which figures and
I'll send the parts.

By the way, here's two comments written by some country somewhere

This bullet is misleading and hardly supported by the evidence given in
Chapter 3. There are virtually no direct objective observations of drought.
Therefore most of the analysis in Ch3.3 is based on a primitive drought
index which depends strongly on precipitation observations. Since drought
is often seasonal, the variability in precipitation and drought is even
higher than in the annual mean, and significant trends are even more
difficult to ascertain. Therefore the statements in this bullet should be
weakened considerably, or the bullet should be deleted.
[Govt. of Netherlands (Reviewer's comment ID #: 2014-8)]

What drought doesn't depend on precip !!!! Is this country somehow different?

This bullet is misleading and therefore unacceptable. As an example we may
take the SAHEL precipitation trends as shown in figure 3.13 in Chapter 3.
For the period 1901-2005 a significant drying trend is shown. For the
period 1979-2005, during which a much stronger anthropogenic warming was
present, a significant positive trend in the SAHEL precipitation was
observed. A closer look at figure 3.13 shows that there are very few
regions in the world with a significant trend with the same sign both in
the period 1901-2005 and in the period 1979-2005. We repeated this trend
exercise for the CRU data set and found again conflicting results.
Apparently, regional precipitation is too variable, to detect robust trends
in precipitation in most parts of the globe. This bullet should be
completely rephrased or deleted.
[Govt. of Netherlands (Reviewer's comment ID #: 2014-7)]

Another odd comment.... We are tied though as for the whole obs chapter, we
weren't allowed to say.. can be confirmed by models, or .. as expected from
increases in greenhouse gases. There is no attribution statement anywhere
wrt the Sahel.. Nice to see this country using the CRU data ....

Don't pass any of this on .....


At 15:35 12/01/2007, you wrote:
>Dear Phil & Keith,
>Thanks for the update and thanks for the figure.
>Would it be possible to have the IPCC 'observations' too?
>Cheers, Gerard
>>> Gerard,
>> I've been talking to Keith about PDSI and I showed him the
>> figure attached. This is one from a Kevin Trenberth talk, so
>> Aiguo Dai probably produced it. Don't pass this figure on.
>> I talked to you earlier about the IPCC CH 3 and the comments
>> we'd had on the drought section. These comments said one thing
>> mainly. PDSI is no good because it calculates evap crudely.
>> Harry will have a revised CRU TS soon - up to jun 2006. He will
>> also have calculated Penman PET for each of the land squares.
>> What I would want to see in a paper is the following:
>> 1. Direct comparison of PDSI (with sc version) with Thornthwaite
>> and Penman PET - to show it makes no difference.
>> 2. Major PC patterns of scPDSI (now with Penman)
>> 3. Like the ppt, showing the effect of temperature. Dai has
>> got a bigger effect by - I think - basin the temperature on an
>> earlier period (say 1951-80 as opposed to 1961-90). Is this
>> effect too big? - probably
>> Any paper will need a few new runs
>> - with the new data
>> - fixing T at some level (1951-80 or 1961-90). Latter better, but an
>> earlier cooler
>> level will enhance the temperature component
>> - Penman instead of Thornthwaite
>> - fixed T, so no temperature component (depends on the base)
>> Perhaps we can discuss this over the coming few weeks. Harry
>> should have all the data ready by the end of Feb.
>> Need to et soils everywhere, but Keith tells me you have that and it looks
>> good.
>> Cheers
>> Phil
>>Prof. Phil Jones
>>Climatic Research Unit Telephone +44 (0) 1603 592090
>>School of Environmental Sciences Fax +44 (0) 1603 507784
>>University of East Anglia
>>Norwich Email
>>NR4 7TJ
>Gerard van der Schrier
>Royal Netherlands Meteorological Institute (KNMI)
>dept. KS/CK
>PO Box 201
>3730 AE De Bilt
>The Netherlands

Prof. Phil Jones
Climatic Research Unit Telephone +44 (0) 1603 592090
School of Environmental Sciences Fax +44 (0) 1603 507784
University of East Anglia
Norwich Email

Attachment Converted: "c:\eudora\attach\Ch03_FinalDraft_Text_TSU_FINAL.pdf"

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