A bit more gnawing on the Stern bone

JA wigs me on having said Stern appears to have got one thing right... he has taken the IPCC view as standard, slightly updated. That was pre-report, based on a quick flip through the consultation paper. But on closer inspection I now see that he is touting the CP.net stuff even there... although far more subtly: rather than this "Several new studies suggest up to a 20% chance that warming could be greater than 5°C." that is so prominently displayed in the review, there were just some graphs buried away; and those were preceeded by 2.2-3.6 for 550 ppmv based on Hadley models (whereas in the report, a third column based on "11 studies" bumps that up to 1.2-9.1).

The main point of Stern science (other than my prior quibbles about the SLR) appears to be the climate sensitivity, and/or T change to 2100. And how these feed into the economics models. I found this info quite hard to find.

After much searching, I find the T scenarios fed into the economics model: This is designed to give outputs consistent with the range of assumptions presented in the IPCC Third Assessment Report (TAR). The scenario produces a mean warming of 3.9°C relative to pre-industrial in 2100 and a 90% confidence interval of 2.4 - 5.8°C (see figure below) for the A2 emissions scenario used in this exercise. This is in line with the mean projection of 4.1°C given by the IPCC TAR. The IPCC does not give a probability range of temperatures. It does quote a range across several models of 3.0 - 5.3°C. The wider range of temperatures produced by PAGE2002 mainly reflects the wider combinations of parameters explored by the model.

I'm not sure that extending the range of T makes any sense. But as pointed out by others (TW), using just the A2 scenario certainly doesn't. And then by pushing at the feedbacks, he gets to 2.6 - 6.5°C, and cautions "these results should be treated as only indicative of the possible potential scale of response" (does that caveat make it into the press releases?).

So Sterns basic science is not too far out. He is picking the high-ends of various ranges though, which doesn't really seem neutral to me. But unlike the sillly HoL people he hasn't made any gross howlers in the science (as for the economics, I don't know).

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OK, I'm desperately trying to understand Stern, and failing. Things just don't seem to connect together properly. Possibly if I actually read the entire thing carefully... but who has the time. So, if anyone can explain to me: Stern sez: Using the results from formal economic models, the Review…

My impression from the press release is that Stern is talking about economical risks: "Taking these together, the Review estimates that the dangers could be equivalent to 20% of GDP or more". If you are trying to estimate the worst case scenario (as the 20% figure refers to), it seems appropriate to use the high-ends,

[I don't think you can justify usin the high ends. You have to use a distribution, weighted by some estimate of its probability. Getting the probabilities is of course difficult -W]

The worst case scenario is that the temperature will grow up to the Planck temperature which is about 10^{32} kelvins, the highest temperature that can exist according to the laws of quantum gravity. The worst case for the global cooling is 0 kelvins, about -273.15 Celsius degrees. Lasers can circumvent this limit by having inverse population and negative temperatures.

These limits are extremely fundamental for fundamental physics but they are less important for low-energy, low-brow sciences such as climate science. So I think it might be a good idea to stay with rational estimates of the temperature changes per century such as 1 Celsius degree or less instead of producing weird combinations of numbers that have no practical consequences.

Links to about 10-20 articles criticizing the Stern report can be found at the end of


[You really need to find some more links from scientists about the science, rather than the economics. And finding people who say the-ipcc-is-all-nonsense doesn't help your cause - W]

NEgative temperatures? You mean less than 0K?

(Yes, I know Motl is barking.)

Putting on my more intelligent head, it seems to me that taking the higher temperature ranges as the possibilities to crunch through the economics is what will open Stern up to a lot of flack. It would probably have been better to just take the standard IPPC projections.
As for the economics, (I am no economist) forecasting is always difficult because of everything from technological change to what looks like me an extremely imperfect understanding of the relationship between physical real resources (Eg dams, mineral ores, etc) and the economy.

From what I've read, Stern is maybe going 1/10th as far as Lomborg did on the other side. But the skeptics (esp the pseudo-intellectual Lubos types) would have us think Lomborg should be a Nobel Laureate in Economics.

From my readings what Stern has to say about the economics of how we mitigate are fine. Cap and trade or carbon taxes, Pigouvian taxation: all entirely standard stuff.

What I think he fails to prove is that we either need to or should mitigate, that's where I think the economics gets a little dodgy.

From what I've read, Stern is maybe going 1/10th as far as Lomborg did on the other side.

That's probably a fair comment. But note that Lomborg is just some random bloke touting a book, he wasn't commissioned to write a report for the Govt. I think it's reasonable and appropriate to hold Stern to a higher standard, and the reason I rarely comment much on the septic stuff is not because I have any sympathy for it but rather because I haven't got the patience and appetite for it that RC (for example) appear to.

Every time James convinces me to relax, I come across another possible mechanism for faster feedbacks (sigh) and have to wonder if, whatever the mechanisms might be, they all have to be subsumed into 3 degrees sensitivity, or if there's a surprise lurking somewhere yet.

This bit is from 2004, before ocean acidification became recent news, when the worry was only that human intervention by dumping lots of iron into the ocean might backfire by boosting first diatoms, then the bacteria that prey on them, a not unlikely scenario.


I found this, which may be the background for why diatoms have a rather large role in carbon cycling:


Science 13 September 2002:
Vol. 297. no. 5588, pp. 1848 - 1850
DOI: 10.1126/science.1074958

A Proton Buffering Role for Silica in Diatoms

Allen J. Milligan, François M. M. Morel*

For 40 million years, diatoms have dominated the reverse weathering of silica on Earth. These photosynthetic protists take up dissolved silicic acid from the water and precipitate opaline silica to form their cell wall. We show that the biosilica of diatoms is an effective pH buffer, enabling the enzymatic conversion of bicarbonate to CO2, an important step in inorganic carbon acquisition by these organisms. Because diatoms are responsible for one-quarter of global primary production and for a large fraction of the carbon exported to the deep sea, the global cycles of Si and C may be linked mechanistically.


..."Should the phytoplankton community shift from P. antarctica to diatom dominance in response to enhanced upper ocean stratification, the capacity of the biological community to draw down atmospheric carbon dioxide could diminish dramatically," Arrigo said in a recent article in the journal Science.



"... ocean life may be more sensitive to climate change than previously believed because most global warming predictions indicate that major ocean circulation patterns will change. While oceanographers have identified many ocean circulation patterns, the study found that three-quarters of all biological activity in the oceans relies on this single pattern.

"When we shut off this one pathway in our models, biological productivity in the oceans drops to one-quarter of what it is today," said Jorge Sarmiento, a Princeton oceanographer who led the study published in the Jan. 1, 2004, issue of Nature. Marine organisms account for half all biological productivity on Earth.

By Hank Roberts (not verified) on 06 Nov 2006 #permalink

OK, if we hold Stern to the standards of other gov't reports (Hutton inquiry; and the Iraq War "45 minutes for Saddam to strike London"); then it comes out as good as gold! ;-)

What does HoL mean?

[House of Lords - W]

Carl, thats why I'm not too much bothered about Stern, gvt reports have some dodgy histories. He has been getting flack for his discount rate, and for taking the highest temperatures. As far as I (A mere member of the public) am aware, this is early days in mere economic accounting for AGW. If it was just a matter of money to us, I wouldnt quite be so bothered, its the long term effects on ecosystems that has me worried, not to mention that we simply do not know enough about the likely outcomes to be complacent.


you say "...its the long term effects on ecosystems that has me worried,..."

you're concerned about an earth that is moving ever so slightly toward a tropical eco system (mental picture) from an arctic eco system (mental picture)?

The terms arctic and tropical ecosystem are not exactly very well defined, are they?
Not to mention that taking the earth as a whole like you seem to be doing is a bit silly.
There was an interesting post by Carl Zimmer on his blog a few months ago about a study which looked at hundreds of species of animal, and came to the conclusion that there would be a very high extinction rate, due mainly to habitat loss brought about by climate change, IIRC.
We humans are already putting tremendous pressure on a lot of ecosystems- they can recover given time, but it is not clear if we will give them that or not.
Another example, look at ocean acidification and coral reef bleaching.

Oh, I haven't noticed your comment previously. I think that the next IPCC report will differ from the previous one so strongly that the opinion that previous IPCC was all nonsense will become rather manifest.

[Did you really not take the precaution of downloading a pre-release copy? Probably one of your colleagues will have access to one. Unless it changes a lot in review, you're quite wrong - W]

Stern Report is a report by an economist and it is about economics, so I find it obvious that in this particular case, other economists are the primary people who have the expertise to judge it. Do you really have any doubts about this thing? The only thing how the report depends on science is that he takes the high-end estimates of various quantities from some people who call themselves scientists. That's not a terribly close link with science.

I have seen a bad version and a better version, plus many reasonable people who are influencing. At any rate, it doesn't matter: if the new IPCC will be the same crap as the previous one, the people who say that IPCC is all bad are simply correct, so what's exactly your problem?

Is that what you string theorists call peer review "the same crap?" You are so deluded I can only imagine your ancestors welcomed Adolph to "liberate" your homeland.

See, Carl, what we're not smart enough to realize is that Lubos is working his hot air to sweep aside the morons in climate science, and replacing them with the knowledge in his huge, beautiful brain.

He will come up with his own manifesto, named after his speaking voice: Grand Unified String Theory of Climate Reality, Alternate Proof.

Everyone STFU. Lubos has spoken. Learn from his wonderfulness. What's the matter with you people, can't you see how wonderful he is?



[Ahem. Sorry folks, can we all aim for politeness please? If you want to diss Lubos, be brave and do it over on his blog - W]

Dear William, I hope that you are grateful to me that I have once again revived your blog and brought all these very nice people to you - Eli Rabid, Dano, Carl etc. At least I guess that you must think that they're nice if they believe almost the same intelligent theories about the climate as you do. ;-) You can use them as a mirror!

Lubos' kiss
The Czech's embrace
The purient string theorist's defiling touch

And do you like the Harvard Physics Department

No, not much

(Apologies to A. Huxley)