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Lumifer comments on Argument Screens Off Authority - Less Wrong
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The anti-global-warming measure most commonly advocated as needing to be done immediately (or sooner) is reduction in fossil-fuel use. So far as I can see, this isn't politically convenient for anybody.
Beyond that: sure, it's worth distinguishing between "do experts agree that AGW is real?" and "do experts agree that AGW is real and likely to produce more than a 2degC rise over the next 50 years?" and "do experts agree that we need to cut our CO2 emissions substantially if the result isn't going to cause vast amounts of suffering and expense and inconvenience and death?" and "do experts all predict exactly the same best-guess curve for temperatures over the next 50 years?" and all the other questions that one might ask.
Eliezer's original nomination of global warming as something not to try to work out on one's own was from back in 2007, and slicedtoad's claim that "experts don't agree" is from yesterday. There's been a shift, over the years, in the commonest "skeptical" position on global warming (and hence in what question we might want to ask) from "it probably isn't happening" to "well, of course it's happening, everyone knows that, but it probably isn't our fault" to "well, of course it's happening and it's our fault, everyone knows that, but it probably won't be that bad" to "well, of course it's happening, it's our fault, and it's likely to be really bad, everyone knows that, but major cuts in fossil fuel use probably aren't the best way to address it". I think we're in the middle of the transition between the last two right now. My guess is that in another 5-10 years it may have switched again to "well, of course it's happening, it's our fault, and it's likely to be really bad, and the answer would have been to cut fossil-fuel use, but it's too late now so we might as well give up" which I've actually seen (I think here on LW, but it might have been over on Hacker News or somewhere of the kind).
In 2007, a little digging suggests that the transition from "probably not happening" to "probably not our fault" was in progress, so perhaps the question to look at is "are human activities causing a non-negligible increase in global temperature?". On that question, I think it's fair to say that "experts agree".
Right now, though, the question is probably "how bad will it be if we continue with business as usual, and what should we do about it?". My impression is that to the first part the experts all give answers of the form "we don't know exactly, but here's a crude probability distribution over outcomes"[1] and their distributions overlap a lot and basically all say at least "probably pretty bad", so I'm pretty comfortable saying that "experts agree" although I might prefer to qualify it a little.
As for "what should we do about it?", I'm not sure who would even count as an expert on that. I'd guess a solid majority of climate scientists would say we ought to reduce CO2 emissions, but maybe the nearest thing we have to experts on this question would be politicians or economists or engineers or something. I wouldn't want to make any claim about whether and how far "experts agree" on this question without first making sure we're all talking about roughly the same experts.
[1] Though they don't usually put it that way, and in particular despite my language they usually don't attach actual probabilities to the outcomes.
I don't believe this is true. In particular, I would like to draw your attention to the Stern Review which came out with quite non-scary estimates for the consequences of the global warming even after its shenanigans with the discount rates.
The climate scientists are definitely NOT domain experts on "what should we do about it" and I don't see why their opinion should carry more weight than any other reasonably well-educated population group.
Some quotations from the Wikipedia page you linked to:
And (from the WP page's summary of the SR's executive summary):
I would say that (1) a permanent 5-20% reduction in global GDP sounds pretty bad, (2) a 5-6 degree increase also sounds pretty bad, (3) serious irreversible impacts on the basic elements of life, with the world's poorest suffering earliest and most, sound pretty bad, and (4) it seems that Stern agrees that these are bad since the SR recommends strong early action.
That was rather my point, and in particular I was not claiming that "their opinion should carry more weight than any other reasonably well-educated population group". (Though I think that's slightly overstated. They should be unusually well informed about what "it" is that we might want to do something about, which is useful information in deciding what to do.)
Not to restart the whole debate again, but first, let's separate handwaving (20%, "serious irreversible impacts", etc.) from specifics, and second, to quote the same Wikipedia page
That is not 2020, that is 2200. I submit that anyone who monetizes damages after 2200 is full of the brown stuff.
In general, the Stern Review tried very hard (including what I think are clearly inappropriate assumptions -- see the same discount rates) to produce a scary report to force action now... and it failed.
Originally you said: the Stern Review came out with quite non-scary estimates ("even after its shenanigans with the discount rates"). Now you're saying: the Stern Review came out with really scary estimates but that's OK because it fudged things, e.g. by using too-low discount rates.
The first, if it had been true, would have been good evidence against my statement that more or less all climate scientists say the consequences of business-as-usual would be pretty bad.
The second may be true (I haven't looked closely enough to have a confident opinion) but even if true doesn't give us good evidence that climate scientists don't think the consequences will be bad. (It might indicate that they don't think it'll be so bad, else why not present their true reasons?. Or it might indicate that they're so convinced it'll be really bad that they're prepared to fudge things to get the point across. Or it might be anywhere in between.)
No, not quite. The actual estimates from the Stern Review are non-scary. Indeed, non-scary to the degree that the authors felt the need to add some scary handwaving. But handwaving is not estimates.
Climate scientists are not domain experts in forecasting the effect of environmental change on human society.
5-6 degrees of temperature rise is scary. Economic loss equivalent to permanent 5-20% loss of global GDP is scary.
If you personally happen to be unscared by those figures, whether because you don't believe them or because they're about the fairly far future and your own discount rate is relatively high, fair enough. In that case we simply have a disagreement about what constitutes scariness.
One difficulty here is that many of the things we may reasonably care about are not readily quantified; and any description of unquantified or barely-with-difficulty-quantified things can be dismissed as handwaving.
(But some of those things have less-handwavy more-quantified counterparts in the Report itself: e.g., tens to hundreds of millions of people displaced from their homes by the middle of the century because of flooding, sea level rise, and drought; 15%-40% of land plant and animal species extinct if temperatures rise a further 2degC. Again, how scary you think those things are depends on how much you care about the future, how much you care about people far away, how much you care about biodiversity, etc., and maybe we differ on some or all of them. I find them quite scary. Note that "how scary is this?" is a separate question from "will it actually happen?" and we're discussing the former.)
I never claimed they are. I said only that climate scientists' forecasts for the consequences of anthropogenic global warming are consistently at least "pretty bad". (They are, of course, experts in forecasting what the environmental change is likely to be, which is an important part of the task of forecasting what its consequences will be.)
We probably do. In this context, "scariness" mean willingness to spend resources now for expected mitigation of potential issues in the future. My willingness is lower than the current mainstream opinion and much lower than that of environmentalists.
Handwaving is not just lack of quantification, handwaving is asserting things without adequate support.
For example, I count the phrase "including a wider range of risks and impacts could increase this to 20% of GDP or more" as pure handwaving even though it includes a number.
I don't think we're talking about "caring" in conventional sense. As I mentioned above, this is really about pricing of future risks with an overlay of generational transfer issues.
Just to be clear: The issue here AIUI is whether the Stern Report's predictions, if correct, are scary. If we're on the same page here, you're saying that the prospect of a permanent loss of 5% or more of world GDP, of millions of extra deaths, and of tens to hundreds of people displaced from their homes, does not seem to you enough to justify the cost of the sort of mitigation the Stern Report proposes. Is that right?
If so: OK, fair enough; I'm not going to try to adjust your values. But I suggest that it's probably quite unusual to regard those prospective harms as "quite non-scary", as not "probably quite bad".
I think it's actually somewhat impure handwaving because in the body of the Report there is a little explanation. But that explanation is itself fairly handwavy and in particular it's not at all clear where the figure of 20% comes from.
That seems to me like just one way of expressing "caring about the future". In particular, using "caring" that way seems almost exactly as reasonable as using "scary" in the closely-related way you say you're using it.
Not exactly -- I don't believe the "millions of extra deaths" projections and I strongly suspect that if I were to dig into the data, I would find the 5% GDP loss to be a shaky number.
In general, my position is that the best way to deal with uncertain threats in the future is to make sure future people are wealthy and technologically advanced. As an analogy, it would have been very unwise of, say, Europe in the XVIII century to suppress the industrialization because of concerns over deforestation, smog, and mines' tailings.