Jim Manzi’s Cherry Pick

This follows on to previous discussion of Manzi here. Manzi’s original piece is at The New Republic.

First off, what are integrated assessment models?

The DICE model, developed by William Nordhaus, is a dynamic integrated model of climate change in which a single world producer-consumer makes choices between current consumption, investing in productive capital, and reducing emissions to slow climate change.

… Current carbon emissions add to atmospheric concentrations via a fixed retention ratio, and realized temperature change is modeled by a three-box model representing the atmosphere, mixed-layer upper ocean, and deep ocean. Damage from climate change is a quadratic function of realized temperature change with a 3-degree change calibrated to cause a 1.3 percent world GNP loss.

(emphasis added)

Begging the question, wouldn’t you say?

Jim Manzi bases his approach to the future of the world on the fact that IPCC WG II quotes the results of such models as showing modest impacts of climate change, but those modest impacts are built in. These are not simulations. These are nothing like the physics based models we have in physical climatology. These are guesses.

What does IPCC really have to say about them, other than the graph which Manzi ultimately references?

It is likely that the globally aggregated figures from integrated assessment models underestimate climate costs because they do not include significant impacts that have not yet been monetised. It is virtually certain that aggregate estimates mask significant differences in impacts across sectors and across regions, countries, and locally. It is virtually certain that the real social cost of carbon and other greenhouse gases will rise over time; it is very likely that the rate of increase will be 2% to 4% per year. By 2080 it is likely that 1.1 to 3.2 billion people will be experiencing water scarcity; 200 to 600 million, hunger; 2 to 7 million more per year, coastal flooding.”

I am no great enthusiast for the AR4 WG II report, and they are not entirely free from responsibility for Manzi’s grossly dangerous conclusion. But a fair reading of the executive summary ought to have been enough to dissuade Manzi from using the figure in question. The text which he advises the world to base its entire future is an egregious cherry pick.

Nobody who calls GCMs into question should pay the least attention to the Nordhaus type model, which is grossly underconstrained by theory or observation, and instead is constrained by guesswork.

Manzi takes a different tack, treating IPCC as authoritative. Thus he accepts or claims to accept the WG I sensitivity spectrum, and uses this as cover for picking a single chart out of WG II as representative of IPCC’s impact assessment. But that choice is not representative of IPCC’s impact assessment at all, and is explicitly disavowed in the chapter executive summary.

I hope Manzi will acknowledge his error and change his position.

IPCC Good News, Bad News.

Good news: Pachauri is reappointed for another term as head of IPCC. Whether or not this would have been a good idea under ordinary circumstances, it was pretty much necessary. Anything else would have just encouraged the jackals squealing for blood.

Bad news: Andrew Sullivan quotes Jim Manzi quoting IPCC:

This is the crux of the problem with McKibben’s argument: According to the IPCC, the expected economic costs of global warming are about 3 percent of GDP more than 100 years from now. This is pretty far from the rhetoric of global devastation that McKibben, and so many others, use.

The question raised obviously is the authority of this claim. Did the IPCC make such a claim? In what context? (Manzi does not provide a reference.) Is there any basis for this claim? What is the confidence interval?

For myself, I have always thought of WG I as authoritative, and WG II and WG III as speculative. Much of the damage to the reputation of climate science has emerged from attributing WG II speculation to “climate science”.

I will probably change everything I’m doing in my professional life if anyone can convince me that the 3% prediction is reliable. I think there’s very little chance of that, but Manzi is right on this point: “One of the great strengths of TNR, in my opinion as an outsider, is that it has made a habit of facing up the strongest arguments of its ideological opponents.” Well, I stopped following TNR fifteen years ago on the grounds of its exasperating blindness on middle east policy and a divergence of interest in general, but I support the principle. So, is there really some way to limit the damage to an unmeasurably small modest reduction of growth?

I have to say my BS detectors are pegged on this one. It will be interesting if blame for this really attaches to IPCC.

Amusingly, Sullivan takes the bait:

But since when did conservatives only care about “economic costs”? I respect Manzi’s cost-benefit argument, and his policy pragmatism. But there is a moral dimension to real conservatism, even a spiritual one, that does not treat the planet as something to be used, but as something to be a sensible steward of.

Maybe so. But if we really believe that “growth” remains possible for a century, it necessarily follows that the probability of real environmental crisis is small. This is not despite, but because of, the fact that the economy is part of the environment.

In future, only actual consensus positions should be reported as such by IPCC, please and thanks. Any clues where Manzi got his idea and what we can do about it?

That all said, I like Sullivan’s concluding paragraphs:

The earth is something none of us can own or control. It is something far older than our limited minds can even imagine. Our task is therefore a modest one: of stewardship, the quintessential conservative occupation.

Conservatives do not seek to remake the world anew. We do not hope to impose upon it some abstract ideological “truth” or bring about some new age for humanity. We seek as conservatives merely to live up to our generational responsibility and to care for the inheritance we have in turn been given. This ecological vision is a Burkean one, which is why Toryism’s natural colour is as much green as blue.

Confirming that the present day Republican party is not conservative.

Update: Plenty of sensible caveats (see comments) notwithstanding, I’d be enormously relieved to see that we are talking about a cost of 3% per century. This works out to a hair less than 0.03% per year.

This year’s cost would be 18.3 billion dollars at that rate. Since costs are expected to accelerate, we can refute the estimate if we can find 18 billion in losses this year.

Estimates from the Pakistan flood losses alone range from 9 billion to 43 billion.

Can we put this down to climate change? I think history will do so. But for present purposes it doesn’t matter. All we need to do is find excess weather/hydrosphere/cryosphere related costs. and Pakistan surely qualifies. This means that we are already bearing the brunt of business-as-usual climate change.

That is, if the estimate is correct, this year would be worse than average in terms of climate related costs averaged over the next century. I think that implies changes much smaller than the WG I consensus, which expects accelerating change. Therefore it would appear to be inconsistent with the rest of IPCC.

Note also that in comments Brian Schmidt points out that this appears in AR4 only as a quotation from AR3 upon which some doubt is subsequently cast.

In any case the idea that a problem like climate change separates out linearly from other problems itself seems highly dubious. I retain my opinion that Manzi’s reasoning is based on a very flimsy premise.

Update: The MIT newspaper makes a similar case. The economists really seem to be getting this wrong; that being the case it makes a lot of sense that a lot of hostility is coming our way. Really, if the premise is correct we are totally barking up the wrong tree, but I just can’t imagine what sort of reasoning could support the premise. It certainly makes the resistance to action far more understandable.
Again, my impression that we are paying attention to the wrong part of the puzzle is reinforced. The physical science doesn’t matter if the economics is so far from what many of us expect. Nor does the environmental science.

Manzi’s Folly and Economics in General

Remarkably, an IPCC WGII report (see p 17) shows the “cost” of a 4 degree C temperature increase to be on the order of 3% of net economic output.

Jim Manzi uses this assertion to conclude that Waxman-Markey is a bad idea. I would go further. If 3% were a measure of anything realistic it would be hard to argue for the sort of policy measure that we are all so urgently arguing for. So I can’t provide a counterargument to Manzi. He even goes so far as to address the fat-tail argument (though of course he misattributes it to Weitzman… sigh…) but it’s all calibrated against that 3% .

I think it becomes crucial to track down that 3% and address it. Which makes us all economists, whether we want to be or not. Boulding’s observation seems germane; total capital is NOT actually the integral of net economic output. It’s where our capital stocks are in 2100, not our GDP, that matters. If climate change is marginal, we should let the chips fall where they may, but the conclusion that only 3% of net economic output is at stake seems totally disproportionate to the risks. IPCC or no (and I’ve never been a big fan of WGII) I have a lot of trouble believing it.

Hope to pick this up again at some point.

Update: Nice followup here. UT doesn’t have priv’s to the referenced article, unfortunately. Is this any way to run an intelligentsia?

National Review Gets Real

Can the Wall Street Journal be far behind?

Quark Soup
points out that the libertarian-conservative-republican (US) magazine National Review has a cover article conceding the reality of anthropogenic warming. You have to subscribe to read the article (I intend to read it over coffee at Borders, frankly) but here’s the (current as of this posting) link for confirmation.

Update: The web is pretty cool sometimes. Apparently the author has written in with a link to a PDF of the article.

All they tell the nonsubscriber is this:

It is no longer possible, scientifically or politically, to deny that human activities have very likely increased global temperatures; what remains in dispute is the precise magnitude of the human impact. Conservatives should accept this reality — and move on to the question of what we should do about it. This would put us in a much better position to prevent a massive, counterproductive intervention in the U.S. economy.

By Jim Manzi