I have now read the IPCC’s Summary for Policy Makers (the SPM, here), and wait for the the report of WG1, the ‘science’ bit of the whole AR5, which should come out on Tuesday, our time. The SPM is a summary of the ‘science’ as set out by WG1, but it is drawn up, or haggled over, by civil servants and advisers, rather than scientists — at least, that is my understanding. To be sure of the argument one has to go to the WG1 report, and that will take a lot longer to read.
The haggling took two days, and one of the principals has said, in a tweet, that he only had two hours’ sleep in that time. The haggling must have been over how exactly to paper over the problems that the last six years have provided for the IPCC since the last assessment report. And, of course, to try to deal with the needs of the 190 countries involved in the business, some wanting more drama, some wanting less, some wanting huge sea-level rises through which to ask for help, some wanting some other form of handout.
The haggling is necessary because the governments are all committed to the IPCC and its processes, and by ‘governments’ here I mean the civil servants and advisers who work to and for the Ministers, who are the politically responsible ones. The civil servants and advisers are most unlikely to want the IPCC and its reports consigned to history, whatever the science says — it’s their jobs we’d be talking about — and the outcome, expressed in the SPM, is in consequence a dog’s breakfast.
The last report, AR4, was produced at the peak time of attention for the IPCC (which shared a Nobel prize for it), and its statements were confident and strong: the increase in CO2 emissions was sending temperatures right up, and that would continue. The temperatures were melting glaciers and polar ice, raising sea-levels and threatening low-lying settlements. The effects on temperature of increasing carbon dioxide would be magnified by ‘climate sensitivity’. The computer models projected bad things for everyone.
It was this emphatic warning that led to the Copenhagen Conference in late 2009, which was expected by some to lead to a global treaty ending the use of fossil fuels. That didn’t happen, but AR4 still had considerable power, and had things gone ahead according to AR4 there would by now be something pretty substantial at the international level.
Things didn’t happen that way, so one’s real interest in the new SPM is what the orthodoxy says about the failure of the projections to be followed by Nature.
First, what about the pause in warming (or, some would say, the beginning of cooling)?
The SPM has shifted the goalposts, and now talks about warming since 1950: ‘Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia.’ Yes, maybe, but what about the pause since 1998? Ah, you can find a reference in footnote 5 to the effect that warming has been less pronounced in the last fifteen years. But there is no discussion. It is simply ignored, despite the fact that greenhouse gas emissions have gone up 30 per cent in the same period.
Second, where did the projected warming disappear to?
The favoured orthodox position is that the warming has gone into the deep ocean. I found the B.2 section on the ocean quite opaque, without a take-home message that I could identify. The data are really equivocal about such warming. It looks like an excuse, not a reason.
Third, what is to be said about the ice at the Poles (and in Greenland)?
The SPM says that what is happening in this area displays ‘[m]ultiple observed indicators of a changing global climate’. The Antarctic, which contains 90 per cent of the ice, is dealt with cursorily, but is agreed to be showing increased sea ice, though losing mass overall (which is a puzzle, given that it is a vast frozen area, where the temperature is way below zero most of the time).
Fourth, what about sea-levels?
The SPM says it is very likely that sea levels are rising faster, though the ‘faster’ period is the last 17 years (and there is abundant literature that must make this a debatable claim).
Fifth, what about climate sensitivity?
In a sense this is the core of the IPCC position. A doubling of carbon dioxide would mean an increase of 1.1 degrees Celsius, which is not threatening to anyone — and has assisted over the past century in an improvement in food production and (more recently still) in a perceptible greening of the planet. For those who write the IPCC reports there is a variable called ‘climate sensitivity’ which amplifies the greenhouse gas effect. By how much? Well, no one is sure and there have been at least a dozen papers on the subject in the past year alone. They all differ in their estimate, but they range from a negative effect to a large effect — greater than 6 degrees C. The SPM says that the range is now from 1.5 to 4.5 degrees C, but says (in another footnote) ‘No best estimate for equilibrium climate sensitivity can now be given because of a lack of agreement on values across assessed lines of evidence and studies.’ Nonetheless, it is very confident about most things in this area. Why, it is hard to imagine.
The SPM is an almost indigestible document, and part of the problem is its use of modifiers that purport to have real meaning. To give you the flavour, ‘the following summary terms are used to describe the available evidence: limited, medium, or robust; and for the degree of agreement: low, medium, or high. A level of confidence is expressed using five qualifiers: very low, low, medium, high, and very high, and typeset in italics, e.g., medium confidence’.
Got that? Then add this: ‘the following terms have been used to indicate the assessed likelihood of an outcome or a result: virtually certain 99–100% probability, very likely 90–100%, likely 66–100%, about as likely as not 33–66%, unlikely 0–33%, very unlikely 0–10%, exceptionally unlikely 0–1%. Additional terms (extremely likely: 95–100%, more likely than not >50–100%, and extremely unlikely 0–5%) may also be used when appropriate’.
These numbers don’t have real meaning. They purport to be ‘statistical’ renderings of various forms of ‘We think that…’
So far as I can tell, the SPM was a one-hit wonder, and the mainstream media have moved on, after their predictable responses. I’ll do the same.