The World Bank, droughts, and voodoo economics

Mendelsohn and Saher ‘analysis’ of “The Global Impact of Climate Change on Extreme Events,” cites Roger Pielke, Jr. five times while quoting not one scientific paper focused on droughts!

This paper quantifies the global impact of climate change from several extreme events: local storms, heat waves, cold spells, floods, and droughts…. [C]limate change is calculated to increase the damages from these five extreme events by between $11 and $16 billion [sic] a year by 2100…. Summing the damages in this report with tropical cyclone and severe storm damages from the literature suggests that climate change may increase the overall damage from extreme events by $84 billion or 0.015 percent of world GDP.

Yes, two ‘leading’ economists, Robert Mendelsohn and Gokay Saher, actually wrote an entire paper for the World Bank that came to such a conclusion. It would be laughable were the potential consequences of such misanalysis not so serious.

For the record, when actual climate scientists and agricultural experts look at these and other damages they naturally come to a very different view (see Scientists find “net present value of climate change impacts” of $1240 TRILLION on current emissions path, making mitigation to under 450 ppm a must).

Coincidentally, another just-released study, “The Last Drop: Climate Change and the Southwest Water Crisis,” that actually looks in some detail at the scientific literature for just one region, finds that drought and reduced precipitation in the U.S. SW alone could cost up to $1 trillion by century’s end.


I don’t know who is going to be disdained more by future generations devastated by humanity’s apparent inability to preserve a livable climate — the fossil-fuel-friendly World Bank or the why-bother-reading-the-scientific-literature economics community.

For the umpteenth time, Memo to economists: Please read the scientific literature before opining on the impacts of global warming.

You would think that in any rational world, an “ultimate damage” analysis by the World Bank on “The global impact of climate change on extreme events” including droughts would include multiple citations to the significant scientific literature on droughts and the impacts of reduced precipitation. Or even cite one damn paper.

You would be wrong. The mainstream economics community has been taken over by a form of circular benchmarking, a self-delusion where everybody cites each other and ignores the scientific literature. I would note that the Mendelsohn and Saher cite multiple articles by proponents of traditional cost-benefit analysis for climate impacts, they don’t cite Harvard economist Martin Weitzman’s well-known work calling such an approach into question in this arena (see my post Harvard economist: Climate cost-benefit analyses are “unusually misleading,” warns colleagues “we may be deluding ourselves and others”).

I single out droughts here for one particular reason. I was chatting recently with one of the World Bank’s leading experts on development, someone who ran one of the in-country offices of a big developing country. I was commenting to him about the devastating impact of the intense deluges that hit developing countries in the past year. He told me he thought that the impact of extended drought was far worse than deluges because they lasted so long and went to the heart of the country’s ability to feed itself.


I believe that Dust-Bowlification — combined with the impact on food insecurity of Dust-Bowlification combined with other extreme events — is the single biggest impact that climate change is likely to have on most people for most of this century (until sea level rise gets serious in the latter decades).

Let me run through some of the scientific literature that Mendelsohn and Saher — and whoever reviewed the paper at the World Bank — didn’t deem worthy enough to include in their paper on “The global impact of climate change on extreme events” — even though they saw fit to cite their own work three times and Roger Pielke Jr.’s five times.

“¦the climate change that is taking place because of increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop”¦. Among illustrative irreversible impacts that should be expected if atmospheric carbon dioxide concentrations increase from current levels near 385 parts per million by volume (ppmv) to a peak of 450–600 ppmv over the coming century are irreversible dry-season rainfall reductions in several regions comparable to those of the “dust bowl” era

The irreversible precipitation changes hit the U.S. Southwest, Southeast Asia, Eastern South America, Western Australia, Southern Europe, Southern Africa, and northern Africa.

Note also that this is only 450 to 600 ppm. We’re on track for 800 to 1000 ppm this century on our current emissions path — a path we are sure to stay on if we listen to the likes of Mendelsohn and Saher (see “Our hellish future: Definitive NOAA-led report on U.S. climate impacts warns of scorching 9 to 11°F warming over most of inland U.S. by 2090 with Kansas above 90°F some 120 days a year “” and that isn’t the worst case, it’s business as usual!” and M.I.T. doubles its 2095 warming projection to 10°F “” with 866 ppm and Arctic warming of 20°F).

The NOAA analysis is hardly the only drought analysis available to Mendelsohn and Saher.

  • Back in October, the National Center for Atmospheric Research published a complete literature review, “Drought under global warming: a review,” (See NCAR analysis warns we risk multiple, devastating global droughts even on moderate emissions path). That study makes clear that Dust-Bowlification may be the impact of human-caused climate change that hits the most people by mid-century, as the figure below suggests (click to enlarge, “a reading of -4 or below is considered extreme drought”):

The PDSI [Palmer Drought Severity Index] in the Great Plains during the Dust Bowl apparently spiked very briefly to -6, but otherwise rarely exceeded -3 for the decade (see here).

The large-scale pattern shown in Figure 11 [of which the figure above is part] appears to be a robust response to increased GHGs. This is very alarming because if the drying is anything resembling Figure 11, a very large population will be severely affected in the coming decades over the whole United States, southern Europe, Southeast Asia, Brazil, Chile, Australia, and most of Africa.

The National Center for Atmospheric Research notes “By the end of the century, many populated areas, including parts of the United States, could face readings in the range of -8 to -10, and much of the Mediterranean could fall to -15 to -20. Such readings would be almost unprecedented.”

But hey, Mendelsohn and Saher say droughts will only be contributing a few billion dollars a year to damages in 2100.

Now I suppose these two economists are free not to believe the scientific literature — but then they are obviously the wrong people to do such an analysis. In any case, to not even cite the literature even to dispute it demonstrates a willful ignorance of arguably the greatest threat to most of humanity.


For the record, the NCAR study merely models the IPCC’s “moderate” A1B scenario “” atmospheric concentrations of CO2 around 520 ppm in 2050 and 700 in 2100. We’re currently on the A1F1 pathway, which would takes us to 1000 ppm by century’s end, but I’m sure with an aggressive program of energy R&D we could keep that to, say 900 ppm.

  • The UK Met Office came to a similar view four years ago in their analysis, projecting severe drought over 40% of the Earth’s habited landmass by century’s end (see “The Century of Drought”).

The impact of just the heat stress on agriculture has also been studied in the scientific literature:

“Ignoring climate projections at this stage will only result in the worst form of triage.”

The release explains:

Rapidly warming climate is likely to seriously alter crop yields in the tropics and subtropics by the end of this century and, without adaptation, will leave half the world’s population facing serious food shortages, new research shows”¦.

“The stresses on global food production from temperature alone are going to be huge, and that doesn’t take into account water supplies stressed by the higher temperatures,” said David Battisti, a University of Washington atmospheric sciences professor.

Yes, the Science study is an underestimation of what is likely to happen since it ignores drought and Dust-Bowlification (so yes, technically, this isn’t a drought paper, it is a heat-wave paper, but the World Bank analysis was supposed to include the impacts of heat waves).

The projection of extended if not endless drought for the US Southwest has been studied a great deal:

The serious hydrological changes and impacts known to have occurred in both historic and prehistoric times over North America reflect large-scale changes in the climate system that can develop in a matter of years and, in the case of the more severe past megadroughts, persist for decades. Such hydrological changes fit the definition of abrupt change because they occur faster than the time scales needed for human and natural systems to adapt, leading to substantial disruptions in those systems. In the Southwest, for example, the models project a permanent drying by the mid-21st century that reaches the level of aridity seen in historical droughts, and a quarter of the projections may reach this level of aridity much earlier.

An unprecedented combination of heat plus decades of drought could be in store for the Southwest sometime this century, suggests new research from a University of Arizona-led team”¦.

“The bottom line is, we could have a Medieval-style drought with even warmer temperatures,” [lead author Connie] Woodhouse said.

  • A new Environmental Research Letters article, “Characterizing changes in drought risk for the United States from climate change,” comes to a similar conclusion as the NCAR study, “Drought frequencies and uncertainties in their projection tend to increase considerably over time and show a strong worsening trend along higher greenhouse gas emissions scenarios, suggesting substantial benefits for greenhouse gas emissions reductions.” See especially Figure 4C.

And, as noted above, a new detailed review and analysis of the literature on just the SW alone finds drought and reduced precipitation cost up to $1 trillion by century’s end.


The World Bank paper by Robert Mendelsohn and Gokay Saher, “The global impact of climate change on extreme events,” is GIGO (Garbage in, Garbage out). While they don’t cite a single one of the major studies listed above, they reference Roger Pielke, Jr. 5 times, papers authored or coauthored by Richard Tol 3 times (see “TolGate”), William Nordhaus twice [still need to do my debunking post on his work], and Mendelsohn himself three times!

While they don’t reference one single scientific study focused on drought, even though that is one of the 5 extreme events they are supposed to be examining the impacts of, they have a dozen references on hurricanes and tropical cyclones (over 40% of all their references), although that is not one of those five.

The conclusions are laughable, though deadly serious, and the whole effort is another serious blow to the credibility of an institution still widely criticized for favoring fossil fuel projects over low-carbon projects. The paper notes:

This paper is a product of the Global Facility for Disaster Reduction and Recovery, Finance Economics and Urban Department. It is part of a larger effort by the World Bank to provide open access to its research and make a contribution to development policy discussions around the world.

It is a major embarrassment to everyone who was involved in this project, including the authors, for letting such GIGO be published under the imprimatur of the World Bank.