You’ll find this hard to believe but I get excited about the 1990 First Assessment Report (FAR). It’s very different from wading through the later ones, because it’s remarkably honest, and things are not hidden in double-speak (well, not so much). Scientists behave like scientists and talk of null hypothesis, and even of validating models. Indeed they had a whole chapter back then called “validation”. How times have changed.
This is the short summary of Chapter 8 “Attribution”
Thanks to Alan for sending me this link today (Chapter 8, IPCC FAR).
The “Attribution” Chapter is the part where they try to figure out what “caused” the warming. Chapter 8 says, essentially, “we don’t know, we might never know, our models don’t work, and we can conclude it might all be natural, but then again, it might not.” Got it?
This is in the same era that Al Gore was saying “the science is settled” and “there is no debate”.
What’s clear in 1990 from the FAR was that it was widely admitted that the models were bodgy, and that figuring out exactly what caused the recent warming was very difficult, indeed impossible at the time. There were too many variables, the signal to noise ratio was awful. There were almost no singularly unique points which the enhanced greenhouse effect would produce that we could use to definitively say “Gotcha!”.
Unlike today, when Professors of Climatism repeat “there is no doubt global warming is real” as if it meant something, back then they knew it didn’t.
“Global mean warming for example is not a particularly good signal in this sense because there are many possible causes of such warming.”
Mind you, even in 1990, they try it on anyway, just to see how it looks. They show model runs versus real temps, over a century. The end result of that (Fig 8.1), shows that all else being equal (meaning all the other forcings exactly cancel out) climate sensitivity would be 1 to 2°C. ie: the observational data, even then, was suggesting 1.5 °C and that’s if they were lucky and the Earth’s climate was essentially stable and not otherwise changing. To get a high 4 °C sensitivity, they have to assume some natural cooling effect is coincidentally at work (which is hiding the rampant warming of CO2). With surprising honesty, they also admit that “if the combined effect [of natural factors] was warming then the implied sensitivity was less than 1°C.” Imagine them saying that now… the “evidence is overwhelming”, and climate sensitivity is somewhere between… ah… zero and 5°C.
Sea levels, glaciers, stratospheric cooling: Not proof
These 1990 IPCC scientists also admitted that sea-level rise and melting glaciers didn’t prove a jot, because anything else that warmed the planet would have caused them to rise and melt too.
Both thermal expansion and the melting of small glaciers are consistent with global warming, but neither provides any independent information about the cause of the warming. [p251]
They further acknowledged that while finding stratospheric cooling was very gratifying, it could be due to ozone depletion and volcanic action, and the models could be right about that, but wrong about everything else as well. In a nutshell, “Don’t throw a party about stratospheric cooling”.
“Validation of the stratospheric component of a model while of scientific importance, may be of little relevance to the detection of an enhanced greenhouse effect”
Nowadays, with so little other evidence on the shelf, they’ll take what they can get. Stratospheric cooling has become more popular. (The Australian Academy of Science mentions it three times in the 2010 PR booklet “The Science of Climate Change”.)
Having given up on finding one factor which gave the game away, they considered “fingerprints” of a bucket full of factors. Was there a pattern which could be uniquely “Greenhouse induced”? Alas, there wasn’t an obvious one, but they were hopeful and had a few candidates. The hot spot was of course, an important one, but sadly, not performing.
The hot spot was already missing
The air between 300hpa (high up) and 100hpa (even higher) ought to have been warming over the tropics. But dang, there was no noticeable trend in most of the tropics, and worse, between 10-30°N it was cooling… “which appears to conflict with model results” as they said.” Yes, rather. It was supposed to warm faster than the surface. [page 251]
Humidity is the other marker of the “hot spot” found in the models, and it is supposed to cause a lot of the greenhouse warming above the tropics. It was also thought to be a good detection variable, because the signal to noise ratio is not so tragic. Even so, they concluded that the results were not an endorsement:
“the magnitude of the tropical trend is much larger than any expected greenhouse related change, and it is likely that natural variability is dominating the record.”
The models were known to be bad
Back then, no one was trying to pretend that they had it figured out:
“We know a priori that current models have numerous deficiencies and that even on a global scale the predicted signal is probably obscured by noise.”
“In all cases (different variables, different months) the observed and modelled fields were found to be significantly different. Ie for these tests the null hypothesis of no difference [between models and observations] was rejected and the model signal could not be identified in the observations.”
They hoped they’d get conclusive proof
Back then, the scientists wondered how long it would be before we could see the greenhouse influence. The answer depended on just how influential the greenhouse effect was: if James Hansen’s worst scenario was the “one”, the IPCC 1990 group figured they’d be able to tell by 2002. Things would have heated up enough that quickly. If his most conservative one was right it would be 2047. And if people actually cut their emissions (ha ha) then it might not be possible to figure it out until well into the 21st Century. (Then of course, there was the other scenario — if CO2 made almost no difference, the conclusive answer might take infinitely long.)
It’s obvious from reading the later versions of the IPCC team output, that the FAR stands alone. By 1996, the stakes were higher and the money so much larger that the tone of all the later reports changes and the stories of corruption and last minute changes, omissions, and twists, mark them as more products of politics than rational thought.
H/t to Alan and to Helen (from last year)
The IPCC’s First Assessment Report has been visible only to the “lucky” sods with a hard copy, or access to libraries and photocopiers. I had help from Helen last year to get me some key parts (thanks Helen), which I’ve been working on, and today Alan wrote with the link to Chapter 8 and more.
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PPS: Thanks also to the special helper in Cyprus. A very nice surprise in the mail! 🙂