From Climate Audit via Greenie Watch.
As most CA readers know, a few years ago, I wondered how they knew that 1998 was the warmest year in a millennium – a claim that you don’t see in AR4. Nor, at first (second or even fifth) glance does the assertion, once so prominent, even seem to be addressed in AR4. The Climategate letters offer an interesting vignette. Chapter 6 authors were not unaware of the matter and worked over language on the issue like New York or London lawyers, eventually inserting a clause deep in the chapter that gave them cover, intentionally leaving the issue out of the chapter Executive Summary. On July 28, 2006, Chapter 6 Coordinating Lead Author Overpeck (1154090231.txt) wrote to Briffa (copy Jansen) passing along a question from WG1 Chairman Susan Solomon, asking the reasonable question about what happened to claimes that 1998 was the warmest year, 1990s the warmest decade.
Hi Keith – in our TS/SPM discussions, Susan has raised this question:“In the TAR they spoke of 1998 being the warmest year in the millennium and the 1990s the warmest decade. I don’t see that chapter 6 addresses any of these time scales. I am not saying you should do so – but are you planning to say anything about it and why you aren’t doing so? and if you’re not planning to say anything at all, can you please tell me what you think about it, just for my own info?”Would you please give me your feedback on this, with enough thoughtful detail to hopefully make me/Susan fully informed (a para should be enough).Thanks, Peck
On Aug 1, 2006, Briffa replied (728. 1154484340.txt) with a comment that would not be out of place at Climate Audit (one of the interesting things about Climategate letters is how often they express views in private that are expressed publicly at CA). Briffa:
Now Briffa didn’t leave it quite like that. He continued with the opinion that confidence could be attached to decadal averages that could not be attached to individual years:
Overpeck (728. 1154484340.txt) acknowledged this message the next day, passing it on to Solomon and Jansen:
Hi Keith – thanks. This makes sense to me. I’ll cc Susan so she understands the issue better, and also can advise on any strategy we should adopt to make sure we communicate effectively.thanks againbest, peck
On Sep 1, 2006 (739. 1157138720.txt), Overpeck and Jansen adopted the strategy of inserting some protective language in the chapter text, while leaving it out of the Executive Summary, and urgently requested Briffa to write some language on the matter (it had not been specifically addressed in the drafts sent to reviewers).
As for the 1998/2005 warmest in last 1000 years issue, we suggest adding nothing new to the ES, in line with our chapter policy from Bergen, BUT adding something in the chapter along the lines of: ” There is currently insufficient knowledge to form a consensus on the issue of how the warmth of individual years of the last 100 years compare with individual years of the last 1000 years” Keith, would you like to make a suggestion on the wording and placement?
On Sep 13 (744. 1158180188.txt), Briffa reverted with some language that was carefully crafted to say the least.
Eystein and PeckI have thought about this and spent some time discussing it with Tim. I have come up with the following
Overpeck wrote back the same day ( 744. 1158180188.txt):
Keith – thanks for this and the earlier updates. Stefan is not around this week, but hopefully the others on this email can weight in. My thoughts…
David Rind weighed in (744. 1158180188.txt) as follows (copies to other Lead Authors)::
Jansen (745. 1158204073.txt) suggested a version without Briffa’s casuistic second sentence:
Hi all,My take on this is similar to what Peck wrote. My suggestion is to write:
On Sep 15, 2006, Fortunat Joos wrote that if there isn’t enough evidence to say whether 1998 was the warmest year or not, they should say so.
A little later, Briffa signed off on the revision, noting his own reservations about the original “too clever” language, expressing a slight worry that they had “inserted this late with no refereeing and no justification in the text” – (a scruple that he and Jones didn’t worry about when it came to matters MM):
I do not disagree either – in fact I preferred not to make the “too clever” second statement in my “straw man” as I said at the time. If this is the consensus (and I believe it is the scientifically correct one) then I would be happy with Eystein’s sentence. The worry is that we have inserted this late with no refereeing and no justification in the text. I would also suggest dropping the second “!individual” in the sentence.
On Sep 15 (746. 1158324958.txt), Overpeck decided to go with Jansen’t language on the “all important 1998 sentence”.
Thanks Keith, Tim and Fortunat for your input. We’ll go with what we have then – Eystein’s suggestion minus the second “individual”. Eystein and Oyvind – just want to double check that you’ve deleted that 2nd “individual” in the all important 1998 sentence??Thanks, Peck
In the AR4 Final Version, section 188.8.131.52 ended as follows;
Greater uncertainty associated with proxy-based temperature estimates for individual years means that it is more difficult to gauge the significance, or precedence, of the extreme warm years observed in the recent instrumental record, such as 1998 and 2005, in the context of the last millennium.
AR4 agreed with MM on the “warmest year in 100 years”. Who would have known?Which leads to another question. What caused the WG1 authors to have a more guarded opinion in AR4 about “1998 is the warmest year” than in AR3? What was their justification for modifying the opinion of AR3 (relying on the statistical analysis of MB98-99) that they knew with statistical confidence that 1998 was the “warmest year”? In the penultimate comment above, Briffa observed that there was “no justification in the text” for introducing this more guarded opinion in the conclusion to the section. The obvious location in the text for justifying this more guarded opinion was in the discussion of the MM papers, which had, after all, raised this issue. After the MM papers observed the abject failure of MBH verification r2 statistics in the early segments, even MBH supporters abandoned any pretence that the reconstruction had any “inter-annual skill”. This point is conceded in a couple of Climategate letters though not publicly. But Briffa, as the author of the relevant section, did not concede even this point in the text on MBH vs MM – a point would have provided a small bit of credit to MM. Worse, between the Second Draft (submitted to reviewers) and the Final Draft, during surreptitious correspondence with Briffa, Eugene Wahl, neither an IPCC author or reviewer, inserted a statement that our analysis had a negligible impact – a statement that was contrary to the corresponding Second Draft statement and a statement that was never submitted to reviewers.Ironically, Chapter 6 Lead Authors adopted a key position of the MM papers in respect to individual years (though not yet individual decades) – a position that clearly contradicted MBH98-99 and AR4 – but failed, as Briffa observed, to document the changed view in the running text. SOURCE