January 8, 2009

Science Fiction Down on the Farm

Filed under: Adaptation, Agriculture

The January 9th, 2008 issue of Science, the official publication of the American Association for the Advancement of Science, contains a remarkable article by University of Washington atmospheric scientist David Battisti and Stanford co-author Rosamond Naylor. Science reputedly is the world’s most prestigious refereed science journal in the world.

Not in this case. The article is remarkably bad. A colleague of mine, looking at an advance copy asked, in all seriousness, if this was an editorial rather than a scientific paper. Sorry, I replied, it’s the real deal.

Actually it’s pretty bad science fiction. Good science fiction is at least plausible.

Battisti’s argument seems straightforward. Take all 23 of the climate models used by the United Nations’ Intergovernmental Panel on Climate Change (IPCC). Over a substantial portion of the moist tropics and desert subtropics, there is a 90% chance that average summer (June-August) temperatures in 2100 will exceed today’s record values, resulting in massive rises in commodity prices as a result of extreme food shortages.

You know the paper’s going to be bad from the first sentence: “The food crisis of 2006-2008 demonstrates the fragile nature of feeding the world’s human population.”

Never mentioned is that this “crisis” was largely due to a knee-jerk political reaction—huge ethanol mandates—in response to climate science alarmism. That crisis was caused by papers like this.

There’s a central problem in Battisti’s analysis. It assumes that projected temperature changes will have such detrimental effects because there’s no economic incentive to adapt to the slow climate change that takes place over a century. Apparently people are so stupid that they won’t do this. Instead, the paper states that “…adaptation can be developed globally but will be costly and will require political prioritization.”

What? Check your mailbox. If you live in the ‘burbs or further out, you’ve already received your Burpee seed catalog, you’re going to see a tomato called “Heatwave,” originally developed about ten years ago in response to the need for plants that set fruit on hot nights. This extends the range of our favorite garden vegetable into the tropics and preadapts it to a warming climate.

You can bet that genetic engineers at Monsanto, DuPont/Pioneer and the other big seedsters of the world are already testing varieties of corn that are more water efficient and will set fruit in hotter weather. As it is, corn grows from Minnesota to the tropics. It’s extremely likely that this corn will be developed pronto, as a very close relative—sugar cane—thrives in the hottest moist environments on the planet.

What about soybeans, the largest source of primary protein in the world? The U.S. produces more than any other nation on earth. If we didn’t cram most of them into pigs and chickens, the amount of nutrition from this remarkable crop could feed a substantial portion of the world by itself. They grow from the northern Great Plains down to Mississippi. Yields are about the same in both places. Summer temperatures in Mississippi average 12.5°F warmer than in Minnesota, a much greater mean temperature change than is projected by the IPCC. Further, beans in general are pretty good at tolerating both heat and drought (which is one reason why Mexican food is so tasty!).

If it really got warm, much of our agriculture could switch to grain sorghum, another great source of carbohydrate and protein. Right now, you’ll find it growing largely in hot, dry climates, because it likes hot, dry climates. And that’s without any genetic engineering to make them it even more adaptable.

The first example of global warming horrors that the authors cite is the 2003 summer heat wave in Europe, which they say is “one of the deadliest climate-related disasters in western history.” Their citation? An unrefereed grey literature publication from an environmental advocacy group, the Earth Policy Institute.

They forgot to mention that there was a similar heat wave in France in 2006. In 2003 there were more deaths than should have occurred, according to heat-mortality models. By 2006, in a similar heat wave, there were far less—mortality was so relatively low that few people outside of Europe are even aware that there was a 2006 summer heat wave.

What happened?

People adapted. We see the same thing in the United States. It would have been nice, at this juncture, if the authors had cited a voluminous literature, mainly authored by University of Virginia’s Robert Davis (admittedly, I am a co-author on many of these papers), which shows something that will surprise no economist but apparently is shocking to climatologists: the more frequent urban heat waves become, the fewer people die from them. There’s gold in the hills of adaptation to climate change, and cities have been warming compared to their countryside ever since there have been, well, cities.

And so does agriculture adapt.

Take a look at our figure below (Figure 1). It shows U.S. corn yields since 1900 along with global temperatures from the IPCC. Temperatures rose about 1.6°F. In 1900, the average corn yield was about 30 bushels per acre. The national average is now around 150, a 500% increase! Global warming sure is bad for agriculture in the world’s breadbasket.

Figure 1. U.S. annual average corn yield, 1900-2008 (top), global annual average surface temperature, 1900-2008 (bottom). (Data sources: National Agricultural Statistics Service; Climate Research Unit).

Apparently that doesn’t matter, because Battisti and Naylor’s paper say this: “It will be extremely difficult to balance food deficits in one part of the world with food surpluses in another.”

Huh? OK, it’s a little outside of their field (my [PJM] PhD thesis was on climate and agriculture), but there’s this thing called a market. If there weren’t, almost everyone in New York would be malnourished.

Will today’s poor nations be able to afford food that they can’t produce for any reason (including climatic)? Indur Goklany, author of The Improving State of the World, assumes the absolute worst about global warming—temperature rises to the max, an unbelievably low discount rate—all the bad things assumed in Britain’s influential (and wrong!) Stern Review on climate change. He still finds that today’s developing nations—largely in the same places projected to experience today’s record temperatures as average—will have twice our current GDP per capita (in constant dollars) by 2100. Think they’ll be able to afford our corn (or soybeans, or sorghum)?

We forgot to mention one other little problem. The average warming given by the IPCC in the scenario used by Battisti and Naylor is almost certainly too high.

Figure 2. Models runs (thin colored lines) for the 21st century under the SRES A1B middle-of-the-road emissions scenario and observed temperatures (red circles) along with the extension of the observed trend (since 1977) to the year 2100.

The 23 different models share a common characteristic. They produce, in ensemble, a constant (rather than an increasing) rate of warming. And, indeed, the warming that began in the mid-1970s is remarkably constant in the statistical sense (despite a lack of net warming since 1997) at about 0.16°C per decade (see our Figure 2). Their median scenario is around 2.6°F. To get to that value by 2100 would require a violation of the central tendency of the models, which is a constant rate of warming. If that’s the case, then the models are pretty much useless, anyway.

My colleague was right. Science has just published bad science fiction hiding as a rigorously peer-reviewed paper. No serious reviewer who is a serious student of global warming would let such document stand unless he or she wanted to for other reasons. Did we mention that the Congress is about to debate global warming legislation?


Battisti, D.S., and R.L. Naylor, 2009. Historical warnings of future food insecurity with unprecedented seasonal heat. Science, 323, 240-244.

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