08 February 2011

Two New World Bank Papers on Climate Extremes

The World Bank has a new paper out by Robert Mendelsohn and Gokay Saher (here in PDF) that focuses on:
the global impact of climate change from several extreme events: local storms, heat waves, cold spells, floods, and droughts.
They conclude that with respect to these events:
Given empirical evidence about the link between climate and damages, climate change is calculated to increase the damages from these five extreme events by between $11 and $16 billion a year by 2100. There is little supporting evidence that climate affects deaths from these events (except for the possibility of local storm deaths increasing).
Note that work that I have been involved in on floods assumes that damage increases proportionally to increases in population and wealth, whereas they find a relationship that is less than proportional. Their findings are of a very small impact (0.015% of global annual GDP when combined with the tropical cyclone results discussed below).  They contrast this result with that of the 2006 UK Stern Review (which I have also criticized here in PDF):
These values are completely consistent with estimates in the literature per extreme event. However, they are completely inconsistent with values stated by Stern (2006) who suggests that extreme event damages could be 0.5 to 1.0 percent of GWP by 2050. Oral statements by Lord Stern even suggest values as high as 5 percent of GWP by 2200. The Stern analysis has been criticized because it confuses changes caused by what is in harms’ way (baseline changes) with what is caused by climate change (Pielke 2007b). But even this mistake cannot justify the estimates by Lord Stern. The hypothesized damages quoted by Lord Stern are completely inconsistent with empirical evidence.
A second study, by Medelsohn, Kerry Emanuel and Shun Chonabayashi (here in PDF), focuses on the future impact from tropical cyclones. They conclude that
Using the minimum pressure damage model, the estimated impact of climate change on tropical storm damages ranges from $28 to $68 billion USD/yr (0.005 to 0.012 percent of GWP) by 2100. This represents an increase of between 50 percent and 122 percent over future baseline levels. Climate change is expected to double the damages from tropical cyclones by 2100 by $54 billion USD/yr. The findings confirm the results of earlier tropical cyclone studies that relied on cruder methods.
Score one for cruder methods (here is one such study in PDF).  They also project that deaths from tropical cyclones will fall, due to projected changes in Myanmar and Bangladesh. 

How much confidence should we place in the projections of the future from these studies? Make no mistake, they are quality research projects from top scholars, but the answer is essentially zero confidence. These studies tell us something about what is possible, not probable. Both papers are very up front about inherent uncertainties -- as the first paper notes:
All the estimates presented in this analysis are inherently uncertain. Each facet of the integrated assessment model is uncertain. The emissions scenario, the climate scenario, the change in extreme events, and how damages might change are all uncertain. A sensitivity analysis is performed for the five events in this study. The results tend to be very sensitive to the climate scenario and assumptions about the damage function. Unfortunately, the analysis could not test the importance of the emission trajectory or the link between climate and extreme events.
What this inherent uncertainty -- perhaps better characterized as inherent ignorance -- means of course is that strategies of robust decision making make good sense. That is to say, with respect to preparing for future extreme events, we should emphasize those strategies that are insensitive to uncertainties. Perhaps the most robust finding of each of these studies (and the broader literature) is that future damages will increase regardless of the the effects of human-caused climate change. Thus, improving adaptive capacity is a no-regrets course of action.

Interestingly, the findings of the paper on tropical cyclones project a doubling of damages by 2100, a scenario that we explored in a recent paper, finding that under such a projection, detection of a human-caused climate signal would take many, many decades at best, perhaps centuries. These studies underscore the fact that efforts to try to pin claims of attribution of recent events to greenhouse gas emissions are empirically groundless, even if symbolically and emotionally satisfying. We are going to have to proceed into the future without knowing the influence of greenhouse gas emissions on extremes. That uncertainty need not stand in the way of making effective decisions about adaptation and mitigation.


  1. The genius of humanity has been and will continue to be adaptation. We survive cooling, and thrive in warming.

  2. Pleasing to see they take Stern to the cleaners.

  3. Hi Roger,

    Good stuff, as usual.

    I think a very good paper would be to look at some recent floods (e.g. Brisbane, the 1993 Mississippi and Missouri River floods, possibly some others) and to ask the question: "If it were possible to deliberately flood certain areas to spare other areas, would that have lowered the flood damage? And by how much?"

    I'm pretty sure the answers would be that the flood damage would be lowered, and by a substantial dollar amount. The idea would be to flood farm land or sparesly populated land, in order to protect more densely populated land.

    I'm pretty sure the answer would be, "Yes, it would have been possible to significantly reduce monetary damages by diverting flooding to less valuable lands." (As I recall, this was in fact done to some extent in 1993, by deliberately breeching levees.) What I envision is something similar to the current situation on overbooked airline flights, where some people are compensated for taking a later flight.

    If you're interested in researching and writing such a paper, I'd be very interested in working with you on both.

  4. .

    "All the estimates presented in this analysis are inherently uncertain."

    Ah, yes. Predictions are uncertain, particularly when they deal with the future.

    That said, a predictive model that predicts winters without snow, as well as moderate snow, and multi-century record breaking snowfall is pretty much useless as a prediction tool.


  5. -3-Mark

    Thanks ... from what I gather this exact question is being raised in the context of the Brisbane floods in terms of the trade offs between flooding rural lands and the risks to the urban center.

    In principle, this sort of question can be addressed with a flood model such as HAZUS for specific basins with the ability to modulate flows.

    It'll be interesting to see the Queensland Inquiry report at the end of the summer.

  6. People only acknowledge that the emperor has no clothes when an important and prestigious organization says so. In this case it is the world bank, an organization that has itself been implicated in intellectual corruption if not financial corruption. It is unusual for one big organization to attack the credibility of another. Usually they cover for each other. We currently have the spectacle of the National Academies of Science putting out ideological junk concerning climate change and energy. The National Academies bill themselves as the science advisor to the government. If the advisor has been captured by ideological fanatics what are we left with? Could it be that the science sector of the economy has grown too big and there are too many weak scientists struggling to publish papers and get attention and they are all covering for each other. The science establishment is not going to reform itself.

  7. ".. work that I have been involved in on floods assumes that damage increases proportionally to increases in population and wealth, whereas they find a relationship that is less than proportional."

    This is interesting. Although I have never lived on a seacoast, I managed to misspend the most wonderful years of my adolescence around Lake Ontario and the St. Lawrence. One thing I noticed about the summer places in the area was that there seemed to be two kinds of design: The huge windows and dozens of bedrooms, wet bar on the dock, and easily-shuttered, steep-roofed, small but concrete-backed dock.

    This indicated to me at the time that some of the "summer people" understood the real danger to their investment -- river ice and snow load -- and others were clueless. The showy places were torn up after a decade; the more conservative designs are still around.

    One would think, in a sane and rational world, the more money one sank into a development in an area subject to natural hazards, the greater the percentage of that money one would spend on protection of the investment against those hazards. But that doesn't seem to be the case, to any statistically significant degree.

  8. They use the Emanuel 2005 hypothesis which was subsequently shown to be grossly simplistic by several later papers, which consider temperature differences, wind shear, rather than just absolute temperature. Notwithsatnding that reality has iminged and tropical storm activity has since waned - contrary to the hypothesis. Even Emanuel admits he got it wrong. Elsner even links hurricanes to solar activity now. Clearly it isn't even a vaguely fair reprsesentation of the scintific literature.

    Of course this the kind of narrow insight you'd expect from the World bank, whose previous linear, biased thinking have ruined entire economies, as faithfully described by Stiglitz (for which views he was subsequently removed from the World bank for not toeing the line). And all they can come up with now is "oops - but nobody could have foreseen this disaster". Well a lot of people did, but they were all ignored.

  9. So, even with pyramided "worst case" assumptions, the baddest outcomes are "easily handled, NBD"? Heh.

    Note that the major exclusions to their best efforts to do data-based extrapolation are precisely the areas the WAGGCMs (Wild-Assed Guess Global Circulation Models) put most emphasis on, "because they can't think of anything better" as explanations of climate.

    The reality is they have NO explanation for climate, of course.

  10. As of today (12 Feb.), your two links to the World Bank server does not work correctly. The first link results in "access denied", and the second link results in the first paper you referred to. I find the second paper by accessing to http://www-wds.worldbank.org and searching by the authors' names, though.

  11. -10-Kooiti MASUDA

    Thanks, I see if I can fix!

  12. Global climate is always changing, from warm to cold, dry to wet, and back in an endless cycle that science hardly understands, cannot adequately measure, and cannot predict. People who are "concerned" about this reality of life should move to the equator, or find another planet. The bottom line is that climate change occurs whether we like or not, and there is nothing we can do about it. "Anthropogenic Global Warming" is a politically motivated fraud.

    Personally, I am far more concerned about the 40-mile wide Yellowstone Park caldera blowing up within our lifetimes than about climate change over the next century. Yellowstone explodes about every 600,000 years, and the last time was 630,000 years ago. When it erupts again it will wipe out most of the northwest United States. This "extinction-level event" is a clear and present danger, and there is nothing we can do about it, either, except to get out of the way.

  13. Links to the papers still not fixed, makes it difficult to comment.