Part I: Incoherent Arguments
So during the Luciagate episode, I wandered over to Lucia's to see what she was up to. Read through the comments (especially the second half) to see the result.
Lucia is at least a semiregular reader here, but I can't say I reciprocate. Though she seems a pleasant enough person, she is very much in the grip of the conspiracy theory view of climate science and in particular the idea that McIntyrean hairsplitting is of the essence. I've always been a kind of a top-down guy myself. I find the whole baseball statistics approach to climate tiresome and, sorry, shallow.
So if you go look at the people who took me on, you will see some classic examples of some of the various naysayer species, all getting along, and all saying very different things. There is Kentucky Andrew whose strategy is simply that of a three year old: why? why? why? and prove it! prove it! prove it! Therefore Not the IPCC. This kind obviously has zero capacity to listen to any answers. Even Lucia expresses exasperation with this specimen.
There is the Russian mathematician type. If this isn't just one guy with three aliases, this is the third example of this type I've encountered. There is a rich literature of the mathematics of nonlinear dynamical systems which I have never been able to penetrate. It is amazing that people who accuse us of arrogance make common cause with this type of person whose main point is that I don't know their theorems and haven't read their papers, so who the hell am I to claim I know anything about climate.
My answer is that the relationship between their field and the one we care about is much more remote than they believe, so their theorems avail them naught. They say, well, of course our theorems do not apply, your system is too messy and therefore you know nothing. Therefore we should act as if the sensitivity is zero, therefore Very Not the IPCC. (Since they tend to be emigres from Soviet Russia, they may throw in, Lubos-like, a dig about our supposed Stalinist motivations.)
The third kind is the "throw spaghetti at the wall" type, the one who will wheel out fifteen half-baked arguments for every one you try to refute. This kind seems the most thoroughly trained in political shenanigans. The approach is as common as it is frustrating. They refuse to play by anything resembling the rules of logic, instead resorting to pure polemics. If you score a point of any sort, they will pretend not to notice. Therefore Very Very not the IPCC.
The fourth kind is the tantalizing sort like Lucia herself or others you see on CA or Blackboard. They are polite, considerate, and show every sign of seeing your point. Then they proceed to ignore it or forget it had been made. They are a great pleasure to talk to, at least relatively speaking compared to the other sorts, and they will not actively subvert your appeal to neutral readers. But somehow like in an Escherlike endlessly rising staircase, their pleasant small concessions never amount to a movement of position. Anyway, you will find them stubbornly sticking with Very not the IPCC and now Very Very not the CRU.
Actual debate seems quite unheard of on these sites. You will only find actual debate among people with an inclination to think. The press calls this sort of constructive debate "disarray" or such, by the way. This is one of the most irritating things about the journalistic approach, where rabid certainty is treated as somehow better than, um, reason. In their view, a club of lunatics humoring each other is somehow more impressive than people who constantly challenge themselves and each other.
Now at one point, Eli thanked me for the word "coherence", as a description of what we've got that the other guys ain't got. But I have been mocked by them for using such a big word, a word whose meaning is so non-obvious. Fortunately, I have some examples.
One came up in the conversation at Lucia's. It appears that the climate catastrophe at the Paleocene Eocene boundary yielded an increase rather than a decrease in terrestrial animal biodiversity. It says so on Wikipedia and my attempts to find credible supporting evidence were in fact successful. It appears that the evidence supports this increase in species diversity at the PETM.
One DeWitt Payne uses this to argue that climate crises are good for you if you are a mammal. This set me back for a bit, since it seemed incoherent. Intrinsically, a climate crisis must be worse than a stable climate; it must be a stressor for well-adapted species. But then I noted that it is stressed species with small breeding populations that tend to speciate. So the fact that the number of land animal species emerging from the PETM was larger than the number going in would have to mean the viable populations had been fragmented and diverged. (Whereas the decline in ocean species simply meant that ocean life had nearly been wiped out.) The number of species in non-crisis circumstances is nearly constant. Both increases and decreases in species count demonstrate stress, and both demonstrate decreases in the population of the various species at the time. So rapid climate change is not actually a good thing. It wouldn't make sense, and so it's not surprising that there's an explanation as to why it isn't what happened.
Nature is coherent.
Part II: The Pink Line
So today I found myself thinking about this figure from AR4:
I had seen this figure several times and had long had a coherence problem with it. I had been taught in the 1990s that temperature increases had a twenty to thirty year lag; in other words, to find warming that is inevitable today (even if all emissions ceased instantly) you would extrapolate the roughly exponential black curve a quarter century forward, and read the temperature from there. Yet the pink line in the IPCC figure shows an increase of somewhat less than half that, attributed to Hansen et al 2005. And I had not heard any changes in the estimated warming "in the pipeline". Had I missed a major change in the consensus?
Today, I decided to have a closer look and try to resolve my confusion. It turns out that the Hansen result assumes "no changes in atmospheric composition", not "an abrupt end to combustion". In other words, the somewhat implausible scenario that dust emissions stay constant (since dust settles out quickly) while CO2 emissions go abruptly to zero (since CO2 lasts a very long time) is portrayed. This understates the committed warming, since everyone expects aerosol concentrations to decline as pollution controls get put in place in developing countries and as shifts to non-carbon-based power proceed.
It turns out on discussion with my fellow bloggers that Zeke Hausfather has already thought this through and has reached similar conclusions.
I am surprised and astonished that the IPCC critics have not been all over this, since it amounts to a systematic underemphasis of climate related risk. The pink line should really climb much more steeply. As you will see from Zeke's article, we are already committed to warming very close to the Copenhagen threshhold.
Given how excited IPCC critics get about every case where an aspect of climate risk is arguably overemphasized, you'd expect them to be equally up in arms about this case where the risk is very seriously underemphasized. Perhaps they missed this one. I await the IPCC critics' vigorous and constructive critique of the IPCC's understating climate risks on this graphic.
Anyway, and here is the point, when you have actual scientific knowledge, information from one source or topic can and should influence your thinking on others. Thus a coherent worldview arises. The naysayers on climate change lack a coherent worldview. Their claim is that climate has some magical properties making it unapproachable by science, and that thus very little can be known. But all they know for a fact is that they themselves know very little. Those of us who know enough are uncomfortable with bits of information that don't fit in right. Our experience is that if we look closely enough, there is usually a difference in assumption or nomenclature, not inconsistent evidence. We don't know everything, but what we do know tends to hang together, because we are practicing actual science, not as some philosopher of science would describe it, but as it actually works. Human minds collaborate to produce a robust and coherent view of the world. When we say "I don't believe that" about something or other (even something well argued like for example a Lindzen and Choi result) it isn't bullying or arrogance, though it may sometimes look that way.
What we are doing is relying on the fundamental coherence of nature. It generally all works out in the end.
Image from Wikipedia: Pink Line (Chicago Transit Authority) by Nate Beal, (c) (cc Attribution Generic) 2006
The only thing we can be sure of about the future is that it will be absolutely fantastic. So if what I say now seems to you to be very reasonable, then I have failed completely. Only if what I tell you appears absolutely unbelievable, have we any chance of visualizing the future as it really will happen.
- Arthur C. Clarke (h/t Brin)