Joe Romm tries to make a big deal of the alleged contradiction between Steve Hayward’s 2003 AEI paper, which argued that the IPCC’s emission scenarios are too “pessimistic” (Romm’s terminology), and your 2008 paper in Nature (Pielke et al.), which argues that the IPCC scenarios are too “optimistic.” To Romm, this supposed flip-flop shows how duplicitous “deniers/delayers/destroyers” are, making stuff up as we go, whenever this advances our nefarious purposes.

There are two problems with this supposed “gotcha.” First, neither you nor your co-authors (Tom Wigley and Christopher Green) are under any obligation to ensure that your paper squares with something Hayward wrote five years ago. To suggest otherwise, as Romm does, makes sense only on the assumption that Pielke et al. and Hayward are not independent scholars but mere mouthpieces paid by the same master (or masters) to spout a company line. I fear that for Romm, “denial machine” is no mere figure of speech but an actual conspiratorial enterprise.

The main problem, however, with Romm’s claimed “gotcha” is that there is no inherent contradiction between what Hayward said in 2003 and what Pielke et al. are saying today.

Hayward said that the IPCC’s emission scenarios are too pessimistic because, overestimating economic growth, they also overestimate emissions. Pielke et al. say that the scenarios are too optimistic because, overestimating technology change, they underestimate emissions. The two criticisms are not contradictory, because the same model can overestimate both economic growth and technology change. Indeed, since technology change tends to spur growth and vice versa, a model that overestimates growth is also likely to overestimate technology change.

As it happens, Ian Castles and David Henderson (C&H), the economists whose analysis of the IPCC emission scenarios Hayward quoted in the AEI paper, subsequently retracted part of their criticism [Henderson, SRES, IPCC and the Treatment of Economic Issues: What has emerged? Energy & Environment, Vol. 16, Nos. 3&4, 2005].

Although C&H correctly concluded that the IPCC dramatically overstated developing country GDP growth rates, they later learned from Norwegian scholars Bjart Holtsmark and Knut Alfsen (H&A) that the IPCC made a correspondingly large overestimate in the rates of energy-intensity decline in developing countries. Accordingly, C&H no longer maintain that the IPCC scenarios’ exaggerated economic growth rates necessarily lead to inflated emission projections (see p. 559 of Henderson’s paper).

It is thus doubly nonsensical to make an issue out of your seeming disagreement with Hayward. Not only are you not responsible for what Hayward wrote, but three years ago Hayward’s authorities publicly retracted their criticism that the IPCC overestimated emission growth rates.

C&H remain critical of the IPCC’s use of market exchange rates (MER) rather than purchasing power parity (PPP) to calculate developing country GDP. However, they learned from H&A that MER leads not only to an “overestimation of [developing country] economic growth,” but also to “an overestimation of the potential for energy efficiency improvements in the developing countries.” [H&A, PPP-correction of the IPCC emission scenarios: does it matter? Climatic Change, p. 3]

In short, the updated, corrected version of the analysis underpinning Hayward’s article is quite consistent with the main conclusion of Pielke et al., namely, that substantial “energy efficiency improvements and decarbonization” are “already built into the IPCC reference scenarios.”

Joe Romm tries to make a big deal of the alleged contradiction between Steve Hayward’s 2003 AEI paper, which argued that the IPCC’s emission scenarios are too “pessimistic” (Romm’s terminology), and your 2008 paper in Nature (Pielke et al.), which argues that the IPCC scenarios are too “optimistic.” To Romm, this supposed flip-flop shows how duplicitous “deniers/delayers/destroyers” are, making stuff up as we go, whenever this advances our nefarious purposes.

There are two problems with this supposed “gotcha.” First, neither you nor your co-authors (Tom Wigley and Christopher Green) are under any obligation to ensure that your paper squares with something Hayward wrote five years ago. To suggest otherwise, as Romm does, makes sense only on the assumption that Pielke et al. and Hayward are not independent scholars but mere mouthpieces paid by the same master (or masters) to spout a company line. I fear that for Romm, “denial machine” is no mere figure of speech but an actual conspiratorial enterprise.

The main problem, however, with Romm’s claimed “gotcha” is that there is no inherent contradiction between what Hayward said in 2003 and what Pielke et al. are saying today.

Hayward said that the IPCC’s emission scenarios are too pessimistic because, overestimating economic growth, they also overestimate emissions. Pielke et al. say that the scenarios are too optimistic because, overestimating technology change, they underestimate emissions. The two criticisms are not contradictory, because the same model can overestimate both economic growth and technology change. Indeed, since technology change tends to spur growth and vice versa, a model that overestimates growth is also likely to overestimate technology change.

As it happens, Ian Castles and David Henderson (C&H), the economists whose analysis of the IPCC emission scenarios Hayward quoted in the AEI paper, subsequently retracted part of their criticism [Henderson, SRES, IPCC and the Treatment of Economic Issues: What has emerged? Energy & Environment, Vol. 16, Nos. 3&4, 2005].

Although C&H correctly concluded that the IPCC dramatically overstated developing country GDP growth rates, they later learned from Norwegian scholars Bjart Holtsmark and Knut Alfsen (H&A) that the IPCC made a correspondingly large overestimate in the rates of energy-intensity decline in developing countries. Accordingly, C&H no longer maintain that the IPCC scenarios’ exaggerated economic growth rates necessarily lead to inflated emission projections (see p. 559 of Henderson’s paper).

It is thus doubly nonsensical to make an issue out of your seeming disagreement with Hayward. Not only are you not responsible for what Hayward wrote, but three years ago Hayward’s authorities publicly retracted their criticism that the IPCC overestimated emission growth rates.

C&H remain critical of the IPCC’s use of market exchange rates (MER) rather than purchasing power parity (PPP) to calculate developing country GDP. However, they learned from H&A that MER leads not only to an “overestimation of [developing country] economic growth,” but also to “an overestimation of the potential for energy efficiency improvements in the developing countries.” [H&A, PPP-correction of the IPCC emission scenarios: does it matter? Climatic Change, p. 3]

In short, the updated, corrected version of the analysis underpinning Hayward’s article is quite consistent with the main conclusion of Pielke et al., namely, that substantial “energy efficiency improvements and decarbonization” are “already built into the IPCC reference scenarios.”

Radical rethink is needed on climate-change policy

http://www.nature.com/nature/journal/v452/n7187/pdf/452530a.pdf

and he has an article in The Guardian today supporting the Pielke Jr et al commentary:

The road from Kyoto – The strategy has failed. The world must follow Japan in a radical rethink of climate change policy:

http://www.guardian.co.uk/commentisfree/2008/apr/04/climatechange.carbonemissions/print

Thanks for your comments.

I tell my students to watch out for either/or questions in their comprehensive exams. Academics love them, but in the world of policy the answer is invariably “yes” and so it is here as well.

But lets be honest, in the real world new technologies are going to be necessary if stabilization is to be achieved at levels anywhere close to levels currently deemed acceptable. This is just a fact. Some may not like it, but it doesn’t make it any less true. See the papers by Hoffert and colleagues that we cite for ample support.

Oops. The comment I made above was supposed to be for your Nature Geoscience letter. You can delete the one above.

Sorry about the double post.

Mark

Well, I’m shocked. I don’t know how you could manage to get something that actually has science in it published in a major publication on the subject of climate change projections. Congratulations!

If you want to (and are allowed to) follow up your terrific achievement with another paper that has actual science, I have a good topic.

You could write a paper that recommends that the IPCC should drop its “scenario” analysis completely, and switch to probabilistic predictions of *all* climate forcing variables, with resulting probabilistic predictions for temperature rise.

For example, Figure 10.26 of AR4 has approximately the following methane concentrations (in ppb) in the year 2020 for various scenarios:

B1 = 1920
B2 = 1980
A1F1 = 2000
A2 = 2010
A1T = 2010
A1B = 2020

Those (ridiculous) projections could be replaced by realistic probabilistic predictions, e.g.

5% probability methane concentration will be less than 1700 ppb,

50% probability methane concentration will be less than 1800 ppb, and

95% probability methane concentration will be less than 1900 ppb.

The same thing could be done for each climate forcing (warming and cooling) agent, e.g., CO2, black carbon, sulfur dioxide, organic carbon, etc.

I think this would probably be too much real science for Nature. But you the man! Maybe you can get it published.

Mark

The Pielke et al. piece is seriously flawed and misleading with conclusions that don’t follow from the analysis. As but one example: Five years ago the American Enterprise Institute “proved” that the lowest IPCC emissions projection is too high, and they backed up their conclusion with actual 1990s data, whereas Pielke, Wigley, and Green have “proven” that the highest IPCC emissions projection is too low, and they backed up their conclusion with actual data from this decade. I have debunked the whole thing here: http://climateprogress.org/2008/04/02/nature-pielke-pointless-misleading-embarrassing-ipcc-technology/

02 Apr, 2008 Posted by: Joe Romm