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Climate and Agriculture: We’re Not Dumb

By Chip Knappenberger -- January 8, 2009

University of Washington atmospheric scientist David Battisti and Stanford co-author Rosamond Naylor have an article in this week’s Science magazine that is making headlines across the world.

Why? Because they contend that we are fast heading towards a global food crisis as a result of a future temperature rise projected to accompany increasing atmospheric levels of greenhouse gases.

However, the paper itself is long on rhetoric and short on supporting science, with the conclusions based largely on improper reasoning.

They assume that people will sit idly by and slowly perish as the climate changes around them, doggedly clinging to outdated and failing agricultural practices instead of adopting new crop varieties and farming techniques as the climate warrants. This is known as the “dumb farmer scenario.”

But, farmers aren’t dumb. The development and adoption of new technologies and crop varieties is the primary reason why crop yields have increased many fold over the past century.

Figure 1 shows U.S. corn yields and global temperatures. Clearly a rise in global temperature has not overcome the advances in U.S. corn production.

Yet, Battisti and Naylor think that it soon will.

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).

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).

But again, Battisti and Naylor also think that as heat waves become more frequent huge numbers of people will die as a result. This is a “dumb people scenario.”

Again they are dead wrong. They cite the high mortality associated with the European heatwave of 2003 and want us to believe that the future holds such heatwaves as commonplace and therefore people will continue to die year after year in mass. But such a claim lacks any scientific grounding. In 2006, another heatwave struck Europe and fewer people died than expected (Fouillet et al., 2008). Why? Because people adapted. Across the United States, far fewer people die from the heat in hot places, where summer heat is commonplace, than die in cold places during an unusual heat wave (e.g., Davis et al., 2003). So as heat becomes more common, we should expect fewer deaths. Again, people adapt to the prevailing conditions—we don’t want to die.

Performing a study that fails to incorporate known responses and then touting the results as a valid portrayal of the future is not science, but science fiction.

To read more about the various shortcomings of the Battisti and Naylor article, check out the excellent article “Science Fiction Down on the Farm” posted at World Climate Report.


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

Davis, R.E., et al., 2003. Changing heat-related mortality in the United States. Environmental Health Perspectives, 111, 1712-1718.

Fouillet, A., et al., 2008. Has the impact of heat waves on mortality changed in France since the European heat wave of summer 2003? A study of the 2006 heat wave. International Journal of Epidemiology, doi:10.1093/ije/dym253.


  1. Ed Reid  

    Let me see if I have this right. Corn yields are up 400%. Temperatures are up by <1.5%. It appears that temperature began rising about 30 years before corn yields began rising. Are we to believe that corn yields would have been even higher if temperature had not increased? Or, should we conclude that a 3% increase in temperature would have caused an 800% increase in corn yields. Or is it more likely that the increased atmospheric CO2 is, at least in part, responsible for the increased corn yields.

    Enquiring minds want to know.


  2. Bob Murphy  

    Great post, Chip. You’re probably already aware of it, but in Lomberg’s Cool It I’m pretty sure he shows that for the heatwave in question, more people were spared winter deaths, than additional people died in the summer.


  3. mlynch  

    What I find odd is that historical references to the Medieval Warm Period describe it as a golden age for agriculture in Europe. Yet there seems to be an ovewhelming assumption that warmer means bad. Am I missing something in the science or is this just another case of people reverse engineering the science from their assumptions.
    Mike Lynch


  4. Russell  

    They also seem to be operating under some kind of dumb reader scenario…


  5. Joe Heater  

    Would suggest that since you are looking at farm productivity in the U.S. your comparison should be to U.S. temperatures. The National Climatic Data Center allows you to do that and while I agree with the thrust of the article temperature changes in the U.S. haven’t been that dramatic over the last 100 years. In fact in 2008 mean annual temperature was only .3 degrees greater than the 100 year mean. For those interested, here the link;


  6. ET  

    During the medieval warming, more crops could be grown in Northern climates. Greenland was green. Doesn’t this all simply cancel out any effects of warming. Land that was only somewhat good at growing things because of cold weather should become better at it. More co2 should also help.

    Is global warming simply modern day witch burning behavior?


  7. TokyoTom  

    Chip, it appears that you have deliberately misstated what the Science article is all about, which is precisely about the perceived need to ADAPT to the relatively higher stresses that climate exchange is expected to put on agriculture in the TROPICS.

    In your even less balanced piece at the “World Climate Report” blog, you cast the Science article as designed to call for cap and trade legislation in the US (climate litigation), but this is clearly bogus, as the article instead clearly notes that mitigation will be too little, too late, and expressly calls for attention to and investment in ADAPTATION in the TROPICS.

    NO ONE – and certainly not the Science article – is talking about the people in middle and higher latitudes starving from climate change; rather, agriculture here has generally been expected to see net gains – despite significant disruption and related adaptation resulting from changing temperature and rainfall patterns.

    In temperate zones such adaptation is already underway (and can largely be left to the market), but adaptations developed here simply are not applicable in different climes, including the tropics and subtropics, which in addition are much poorer (and more poorly governed).

    Whether (and how) the West should help poorer countries to adapt to climate change or simply leave poorer peoples in poorly governed nations to their own devices is the real question posed by the Science article; while scientists are unable to answer what are essentially political and moral questions, they do not do us a disservice by raising them.

    You should look in the mirror when you levy charges of meretricious science nonsense, since you are essentially playing shell games with us, by reassuring us that the temperate climes will adapt but failing to address the different, greater and less tractable problems that those in the tropics and subtropics face.

    It is telling that you refuse to link to the Science article or to press releases or news articles discussing it; some of those are here:


    Even those who love what you serve up would do well to recognize that you do not contest the prognostication of further warming and need for adaptation. Further, they should also note that Indur Goklany, the conservative analyst whom Chip refers to at his even less balanced piece at the “World Climate Report” blog, explicitly calls for the Western nations to invest billions in helping the developing nations to adapt to climate change.


  8. ‘Climate and Agriculture: We’re Not Dumb’ Follow-Up — MasterResource  

    […] one of my first posts for MasterResource, I discussed a (then) just-published paper in Science magazine by David Battisti and Rosamond Naylor that argued […]


  9. Alex  

    The increase in corn production is due to improvements in technology such as genetic engineering, pesticides, fertilizer usage, and tractors and mechanical harvesters, as well as government policies. It had little to nothing to do with climate.


  10. cknappenberger  


    Thanks for your comments.

    Two of the historical examples used by Battisti and Naylor were in the extratropics—the heatwave in France in 2003 and the heat in the Ukraine in 1972. The France example was totally inappropriate for the matter being discussed. And completely ignored known and on-going adaptive responses. True, unusual weather events can and do lead to dramatic consequences, but when they become commonplace, people adapt to them—sensitivity to extreme heat is a prime example of this, as you know.

    Battisti and Naylor focus on the tropics and subtropics because that is where their temperature signal first rises above the noise. With time, as the signal grows into the extratropics, Battisti and Naylor expand their concerns to there as well—“Lastly, with growing season temperatures in excess of the hottest years on record for many countries, the stress on crops and livestock will become global in character.”

    The Battisti piece is simply gratuitous alarm-ringing. What good does it do for farmers to take actions for the climate 100 years from now? They need to use the most appropriate technologies (including crop varieties) for today’s climate. If and when changing conditions require different technologies (including crop varieties) these will undoubtedly be developed (as they have been throughout the last century). Expenditures for a potential future climate are only useful if they provide benefits today. There is no reason for a farmer to plant a crop developed for prevailing climate conditions that are different than the current ones, unless that crop is better producing in the current climate.

    Yes, adaptations to climate change are required. And yes, I believe, they will come about as the need for them arises. If Battisti and Naylor’s piece was a trumpet-call for young people to start considering crop science as a course of study, then perhaps they are on to something, if it was a scare-story describing the evils of global warming, then, in my opinion (as you could tell), they were terribly off-base.



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