I have been trawling through some more Climategate 2 emails, and came across a brief exchange (email o222 of 2005). I may be wrong, but I am not sure I have seen this one in the many discussion of the emails. As before, I have tidied up the email by removing symbols such as >>>, and any bold in the text is my emphasis.
cc: “Thomas C Peterson” <Thomas.C.Peterson@noaa.gov>
date: Thu Jan 6 08:54:58 2005
from: Phil Jones <email@example.com>
subject: RE: Fwd: Monthly CLIMATbulletins
to: “Parker, David (Met Office)” <firstname.lastname@example.org>, Neil Plummer <email@example.com>
Just to reiterate David’s points, I’m hoping that IPCC will stick with 1961-90.The issue of confusing users/media with new anomalies from a
different base period is the key one in my mind. Arguments about the 1990s being better observed than the 1960s don’t hold too much water with me.
There is some discussion of going to 1981-2000 to help the modelling chapters. If we do this it will be a bit of a bodge as it will be hard to do things properly for the surface temp and precip as we’d lose loads of stations with long records that would then have incomplete normals. If we do we will likely achieve it by rezeroing series and maps in an ad hoc way.There won’t be any move by IPCC to go for 1971-2000, as it won’t help with satellite series or the models. 1981-2000 helps with MSU series and the much better Reanalyses and also globally-complete SST. 20 years (1981-2000) isn’t 30 years, but the rationale for 30 years isn’t that compelling. The original argument was for 35 years around 1900 because Bruckner found 35 cycles in some west Russian lakes (hence periods like 1881-1915). This went to 30 as it easier to compute.
Personally I don’t want to change the base period till after I retire !
At 09:22 05/01/2005, Parker, David (Met Office) wrote:
There is a preference in the atmospheric observations chapter of IPCC AR4 to stay with the 1961-1990 normals. This is partly because a change of normals confuses users, e.g. anomalies will seem less positive than before if we change to newer normals, so the impression of global warming will be muted. Also we may wish to wait till there are 30 years of satellite data, i.e until we can compute 1981-2010 normals, which will then be globally complete for some parameters like sea surface temperature.
On Tue, 2005-01-04 at 21:58, Neil Plummer wrote:
Hi Hama, Tom
(and David, Blair)
Re: the issue of using the 1971-2000 normals in CLIMAT rather than 1961-1990 normals.
Happy New Year!
I have copied the relevant text from CCl XIII below, which provides reasons for staying with the 1961-90 standard. My initial recommendation is the same as Tom’s, i.e. stay with the standard for now.
I think there are two main factors to consider here – capability and demand. While there are clearly advantages with widespread use of normals derived using the later period there must be the capacity to do so.Perhaps in the lead-up to CCl-XIV, OPAG 2 can find out the extent of the support for the change among users of CLIMAT and OPAG 1 can find out more about capabilities. (Note, however, that this is not strictly on issue for OPAG 1 according to the ToRs for the ICT and any of the ETs. Happy to assist though).
We may use the climate working groups in the Regional Associations to assist with surveying members capabilities and could do the same regarding the demand question though I think Tom’s CCl/CLIVAR ET is best placed to give that guidance.
David, Blair – Interested in your thoughts on this matter.
The email round commenced with a request for a clarification from the Turkish meteorological office on the . I will leave the technical points to other who have a better understanding of the issues that are being discussed. However, I was fascinated to see firstly that Phil Jones was putting confusing the media as a key concern. And then there is the worry of Parker that the impression of global warming would be muted! Note the use of the word ‘impression’. Does this sound like he is worrying about the science?
Again, here we have emails in their context, and the phrases in their full context, and two clear statements that the media and impressions are the priority over the science. Oh dear, oh dear….
Note: Two phrases which are highlighted, I will leave for others to consider who have the technical knowledge to do so.