A Stern talking-to

That name really is a bit of a gift to unimaginative headline-writers.

As jules mentioned, we attended another set of Asahi Blue Planet award talks recently, which you can find out about here. This time both of the award-winners were economists, albeit of a rather different flavour. The first, Uzawa-sensei, gave a rather rambling (but interesting) account of the birth and growth of the concept of Social Common Capital, his idea of how to account for the natural environment and social infrastructure that supports society but was basically ignored in standard economic theory. His talk started with the Papal encyclical of 1891 (!) and got about as far as the Papal Encyclical of 1991 before he sort of ran out of steam (and time) and sat down to rapturous applause. There hasn't been a Japanese winner for some time, and the lecture hall was packed, though this may be due to the fact that climate change is high on the agenda these days. I couldn't help but think that mt would have enjoyed the talk (and blogged more usefully about it), it seemed to be right up his street. There are more details about his work on the web page I linked to above, but it seems that the lectures have not yet been published (they will be eventually, judging from previous years).

Lord Stern was rather more down-to-earth, focussing on facts (ish) and figures relating to the economics of climate change, which will be fairly familiar to people who have read (about) his Stern Review on the Economics of Climate Change. It seemed to me that he was rather too quick to rattle off lists of numbers, probably losing the (general and non-scientific) audience in the process. However, he did provide some pretty clear statements (eg calling for an 80% reduction in emissions from developed countries by 2050, and also pointing out that we'd better start acting rather sooner than that) that probably challenged the (usually docile) audience's complacency and resulted in an unusually lively question and answer session. I'm not talking about riots here, anyone who has been to Japan will realise that the standard experience is a stony silence and at best a couple of anodyne "can't we all get along" suggestions.

I've already complained about the excessively pessimistic approach to climate change that Stern took, and again he included numbers like a probability of 69% that a CO2 level of 550ppm would result in a warming of more than 3C relative to pre-industrial. He also quite clearly talked at one point about the future world being poorer than at present after 2050, despite the fact that all of his analysis is explicitly predicated on compound growth of about 5% per annum for the foreseeable future (specifically, 2.5% in developed, 7% in developing countries). That leaves the world about 4x richer in only 40 years, and none of the climate science credibly suggests mass destruction of the global economy over that sort of time scale and likely ~1C warming. There was also a fair amount of (IMO) magic wand-waving, ie the expectation that all we have to do is impose some tax or cap on carbon (he didn't promote one over the other) and the new technology would come along and save the day. Well, it might do...but it might not! There was also lots of praise for Japan's bold and courageous promises on carbon emissions. I use the terms bold and courageous in the Yes Minister sense, but I think Stern was being encouraging :-) Of course the Japanese are now rowing back as hard as they can (or at least laying the groundwork for a hasty retreat), which should be no surprise to anyone...

In the questions, Lomborg came up, which Stern quite clearly and deliberately dismissed as based on "undergraduate errors" (he used the phrase twice) - specifically, the false dichotomy of Lomborg's either/or approach to addressing the world's problems. On this, I agree with Stern of course. People who suggested that it was unfair for developed countries to take the lead were also given short shrift, though Stern pointed the finger pretty firmly at the USA as the worst offender, and didn't put so much emphasis on the large cuts that Japan (and the rest) would need. However he did not shirk the India/China issue, and dealt with it quite fairly, I think.

RC on Stern

RealClimate have at long last broken their vow of silence on Stern:

"In conclusion: Stern gets the climate science largely right, though he strays on the high side of various estimates and picks the high side to talk about in the summary. This high-end bias lends the Review open to charges of "alarmism"."

If they'd wanted to pick a fight they could probably have been a bit more critical but I'm not going to quibble with that.

Baer on Stern

Paul Baer posted his Comment on the Stern Review on Post-NormalTimes some time ago. I tried commenting but it seemed to vanish in the spam-trap, so I'll comment a little more substantively here instead.

Like many, Paul rejects the Stern Review. However, in his case, it's because he thinks Stern doesn't go far enough. It's a lengthy article which I recommend you to read and make up your own minds over, but I think I've got the essence of it here:

1. Melting the Greenland Ice Sheet would be a "catastrophe"
2. Catastrophes are things that we must do everything possible to avoid
   
3. 550ppm CO2 leaves open a significant probability that the GIS would melt
4. Therefore, we must reject 550ppm as a target
   

In a break from tradition, I'm not even going to complain about his climate sensitivity estimates, as although he does take some of the high climate sensitivity estimates rather more seriously than they deserve, that probably doesn't qualitatively refute his argument. Even with a sensible sensitivity of 2.5C, 550ppm CO2 could result in a large-scale melting of the GIS (based on my understanding of what people think). Of course this is likely to be a glacially slow process. but I don't deny it could happen in the long term.

My complaint is rather that he doesn't define "catastrophe" anywhere (except implicitly as "something we must avoid at all cost"), and therefore doesn't actually go to the trouble of justifying including GIS melt in this category. Nor does he attempt the difficult but necessary step from the idealistic but unrealistic "avoid at all costs" to any analysis of how feasible it is, and what the costs and benefits actually might be. As a result, the whole essay seems to be lengthy illustration of the logical fallacy known as "begging the question".

On a related issue, I was looking through the BBC news pages on Stern, and found these clangers in their summary:

• If no action is taken on emissions, there is more than a 75% chance of global temperatures rising between two and three degrees Celsius over the next 50 years
• There is a 50% chance that average global temperatures could rise by five degrees Celsius
  

I don't have any idea where they might have got this nonsense from, I'm sure it is not in Stern's summary of climate science, exaggerated as that is. I don't believe there is a single active climate scientist who would defend either of these statements, even if the second is interpreted as meaning by 2100 rather than the implied 2050.

From the same page, I also don't believe:

• Crop yields will decline, particularly in Africa

and would be willing to bet against it. That is, I expect crop yields to increase for decades into the future, as they have done in the past (eg random google).

And more subtly, the alert reader will note in the following:

• Extreme weather could reduce global gross domestic product (GDP) by up to 1%
• A two to three degrees Celsius rise in temperatures could reduce global economic output by 3%
• If temperatures rise by five degrees Celsius, up to 10% of global output could be lost. The poorest countries would lose more than 10% of their output
• In the worst case scenario global consumption per head would fall 20%
• To stabilise at manageable levels, emissions would need to stabilise in the next 20 years and fall between 1% and 3% after that. This would cost 1% of GDP
  

that all of the climate-related "losses" and "costs" are presented as the upper end of their uncertainty ranges, whereas the cost of mitigation is a wonderfully confident and precise "this would cost 1%" even though Stern's estimate of the cost of stabilisation is right at the bottom end of all published estimate (even John Quiggin struggles to defend it here: "a range of costs for a 60 per cent reduction in emissions of between 1.8 and 4.2 per cent, with a midpoint of 3 per cent, which is in the upper part of the Stern range").

Uncertainty is a wonderfully versatile thing in the right hands :-)

Update
Well JQ thinks my quotation of him is "tendentious, to put it mildly". So you'd better go and read his whole post and see for yourselves how much of a ringing endorsement he provides. It's not really central to the point I was making on the selective treatment of uncertainty though.