In 1992, the IPCC issued a Supplementary Report to the 1990 Assessment Report, which visited some of the multiproxy topics in chapter C. Again, I’ll provide some extended excerpts: The main summary stated:
Warming over the past few decades is primarily due to an increase of night-time rather than day-time temperatures. These change appear to be partly related to increases in cloudiness but other factors cannot be excluded (p 17)
The Executive Summary to Chapter C stated:
It is still not possible to attribute with high confidence all or even a large part of the observed global warming to the enhanced greenhouse effect. On the other hand it is not possible to refute the claim that greenhouse-gas enhanced climate change has contributed substantially to the observed warming.
There is one page on paleoclimate studies. Cook et al [1991] re Tasmania and Norton et al. [1989] re New Zealand are mentioned with the caveat that:
“no allowance has been made in these or similar studies for the possible fertilization effect of twentieth century increases in carbon dioxide (CO2) on tree growth, neglect of which might lead to an overestimate of recent warming"
Given the dependence of MBH98 results on trees argued to be most affected by CO2 fertilization, it will be interesting to track this issue into SAR and TAR. They report some then recent oxygen isotope measurements from Antarctica as follows:
Oxygen isotope measurements from the northern Antarctic Peninsula have been interpreted as evidence of warmer temperatures during the nineteenth century compared with the twentieth century (Aristarain et al 1990). However the isotope/temperature link is weak both physically and statistically (Peel, 1993) and accumulation rate changes which are more directly related to in situ temperatures point to cooler conditions in the 19th century (Jones et al 1992).
I haven’t worried through oxygen isotope data, but I am very suspicious about overuse of Thompson’s dO18 tropical data, where rain-out effect is conflated with temperature effects. It would be interesting to see exactly why the Aristarain results are dropped from multiproxy studies, while Thompson’s get used canonically. The IPCC then mentions some Chinese studies (Wang and Wang, 1992; Wang et al. 1991) – these turn up in Bradley and Jones [1993] as well. While the 1990 IPCC had been skeptical of tree ring results, Briffa’s Tornetrask study (discussed in detail elsewhere on this blog) gets highlighted next as follows:
Briffa et al [1992] have expanded the analysis presented in an earlier paper [Briffa et al, 1990] where they use tree-ring data to reconstruct summer temperatures for northern Fennoscandia since AD500. Their new analysis is designed to highlight greater than century scale variability which was largely removed by the analysis procedure they used previously. They find good evidence in this region for a Medieval Climatic Optimum (S7, 202) around 870-1110, another warm period around 1360-1570 and a Little Ice Age (S7, 202) period around 1570-1750.
They then refer to new articles on long instrumental series at De Bilt and Central England (van Engelen and Nellestijn, 1992; Parker et al, 1992) and using coral proxy data to reconstruct precipitation in Queensland (Lough, 1991). Section C4 discusses detection and attribution, but does not discuss the question of attribution of past centennial-scale climate change, which had concerned IPCC 1990. They point out that progress in the "fingerprint" detection of an enhanced greenhouse effect is "very difficult" and that no definitive paper on detection has appeared since the 1990 IPCC Scientific Assessment. They point out that:
“it remains to be proved that the greenhouse signal is sufficiently distinguishable from other signals to be detected except as a gross increase in tropospheric temperature that is so large that other explanations are not likely (see S8)."
Climate Audit 
13 Comments
Thirteen years ago Steve…
Such conversations as this were, I think, in their infancy then. Does that mean the internet hasn’t changed since 1992? No, computer technology moves on, so does climatology. But the evidence seen then continues to mount up…
Peter, To paraphrase your generalistion I would say that the cherry-picking “continues to mount up…”
It would be highly frustrating for an honest climate scientist to see how much their field has deteriorated since 1992 or so. Fortunately, there are almost no people who could be frustrated. It’s obvious that the main work related to the attribution of temperature variations has been brainwashing, manipulation, fight against the skeptics, and consensus building. Back in 1992, things seemed to have been a bit more scientific.
C’mon Peter, trying to parallel advances in climatology since 1992 with that of the internet is absurd.
Then again, maybe your analogy isn’t so bad underneath the surface. I can recall when investor after investor jumped on the internet stock bandwagon and made the Nasdaq look like the hockey-stick. It was going nowhere but up, and faster than ever, they said. They laughed at anyone who doubted them. Then lo-and-behold the bubble burst and the hockey-stickers came crashing to the earth.
Re#4, Micheal, you’ll be right if temperatures fall a lot. Care to bet on it? (or indeed you Michael).
Lubos, stick to you dimensions & strings mate 🙂 and stop accusing nearly all climate scientists of dishonesty – grrrrr. Shameful.
Re #6
Shameful would be the behavior of somebody who has already accused the US House Committee on Energy and Commerce of a "witch hunt" and accused its chairman of bias because a few of his donors are from "fossil fuel" concerns. Is that shameful person worried about something?
Lubos did not accuse “nearly all climate scientists” of dishonesty, unless of course, you impute that “honest climate scientists” are few and far between…
Re #6. A new level of political interference, intimidation even, in the workings of science perhaps?
Or would you John A, be happy for some lefty politico to behave in a similar way towards Climate Audit?
RE#5,
I didn’t say temps would drop dramatically sometime in the future…I simply said the occurance of such a thing would be the only reasonable analogy I could find between climatology and the internet.
I actually expect land-based temperature readings to gradually warm for the next several years to up to two decades. I do think we would see some cooling in the land-based readings with a PDO phase shift. Such a thing should likely not have a significant effect on average global temps, but I think it may significantly and disproportionately affect measuring stations and give an appearance of global cooling (just as I think the last shift may have disproportinately created the impression of global warming that really isn’t). And the urban heat island effect will also continue to both increase in magnitude and spread.
I would certainly be willing to wager that if the average land-based measurements of the earth’s temperature are cooler 5, 10, 15, or 25 years from now, you will find blamesayers claim it is “due to global warming.”
Re #7
The political interference, intimidation even, has come primarily from self-serving bureaucracies with a vested interest in keeping methodologies secret while publicizing results which cannot be checked and which fly in the face of lots of other published works.
The Committee has asked questions because it represents the US taxpayer who is paying Mann, Bradley and Hughes’ paychecks, and wants to know why results have not been checked and methodologies kept secret. There is no intimidation implied.
At the end of the day, somebody has to call scientists to account for the money spent. Nobody is suggesting that science should be curtailed for political reasons.
Re#7,
Anyone with a shred of confidence in their work would not have any qualms about responding to the “witch hunt.” It should just be a relatively minor inconvenience of time consumption. I can say that I’ve had to give depositions about the accuracy and validity of my work in the past, and while I dreaded the time spend in front of lawyers, looked forward to and very much enjoyed showing up the opposing side.
“Or would you John A, be happy for some lefty politico to behave in a similar way towards Climate Audit?”
I would welcome “some lefty politico” to behave in such a manner as opposed to the status quo of saying, “We’ll assume the peer review process worked with Mann’s reconstructions.”
The danger is not what you consider “political interference” or “intimidation even.” The danger is a lack of questioning.
Re #10, “The danger is lack of questioning”.
Funny that, give the responses to the only two persistent questioners of this place, myself and John Hunter.
(I sense an ad hom winging it’s way towards me, probably not from you though… You see, I ask the wrong kind of questions…)
Peter, the only questions coming from you are variations on the theme “Why don’t you believe in the prophet Mann and his holy hocky stick?” You only appear to be questioning why the rest of us are asking questions. To be fair, I think you did post something factually related to an actual discussion but that was an extremely rare exception.
I think John H. also posted some stuff that attempted to deal with the facts but it was drowned out by his whining.
Re#11,
I’m not quite sure which questions (specifically coming from you) you are referring to. I don’t ever see you raising questions here about MM’s methodology or work (of course, maybe that’s b/c MM tend to spell things out in gory detail and make such inquiries unnecessary in the first place). I’ve seen John H make demands of Steve that quickly were responded to. That’s in sharp contrast to other researchers who don’t/won’t answer questions, won’t share their source code, etc, or other websites which censor questions such as, “since when is an interpretation considered science?”