unequivocal warming, but not unequivocally human

Interesting quote from Andy Revkin buried deep in his comments section at dotearth:


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There's utter logic in concluding that if there is, as the IPCC concluded, 90-percent confidence that more than half of recent warming is greenhouse-driven, that implies a substantially higher level of confidence (well up toward, if not precisely 100 percent) exists that some greenhouse warming is under way.

But the IPCC -- outside of the questionable line in this chapter -- never stated there was no doubt about human-driven warming. Again, that doesn't mean there's no doubt, given the breadth of evidence. It just means they never formally said it.

I actually had prolonged discussions with both Susan Solomon and Michael Oppenheimer of the IPCC about this after some IPCC authors expressed concern over that very phrase in an update we ran on the latest climate science just before Copenhagen. http://j.mp/noCO2doubt

Using that logic, I wrote that the panel “...concluded that no doubt remained that human-caused warming was under way and that, if unabated, it would pose rising risks.”

They both disagreed:

Dr. Oppenheimer: "The 'no doubt' or 'unequivocal' refers only to the warming part, not the human-caused part."

Dr. Solomon: "This could be true but it's not something that we said."


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Time they reminded some of their colleagues and disciples who regularly use that phrase cavalierly.  The trouble is, the fact of warming does not suggest the cause of it. The warming of the last century though has been a linear trend with fluctuations. We think we know the fluctuations are down to ocean cycles but the trend is not so easy. It could be just another long term fluctuation - as suggested by Avery and Singer in their book "Unstoppable warming every 1500 years". Certainly if 50% of it was natural last century and the trend in the 2nd part is the same as in the first part then the rest of it has a good chance of being natural too, in the form of a natural recovery from the little ice age. The idea that it was manmade was based on a false assumption that we could tease out the natural component from 1985 to 2000 so what was left must be man-made warming. It was a ridiculously optimistic or misleading idea - no doubt entirely to influence policy. The significant pause in recent warming put paid to the idea that natural fluctuations were predictable on these shorter timescales. So to really answer the question of what caused the warming, we really need to first ask the questions a)- what caused the little ice age, and b) what caused the medieval warm period before it, because these were 100% natural and seem to have been global. When we know that long-term natural component then we can tease out the manmade contribution and not before. 


Of course several solar theorists have said the long term trend seems to match solar activity. One that springs to mind was Scaffeta and West who compared solar reconstructions with Moberg's proxy reconstruction. A bit iffy mind you but interesting. The exchange between Scaffeta and Rasmus on realclimate.org was quite entertaining. To me Scaffetta won on points and Rasmus gave up. It didn't help that he got the Stefan-Boltzmann equation wrong; somewhat of a howler for a man in his position. Neither did it help that he was pretending that the now utterly discredited and even disowned hockey-stick reconstructions were better than Mobergs effort.  Nor that his main defense for that was the utterly illogical canard that if natural variation proved large then that is even more reason to worry about CO2 rises.

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