March 22, 2013 5:19PM

Burning Books, Burning Witches, Burning Corn

Global Science Report is a weekly feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”


History is littered with ideology gone awry.

The most recent example? Burning corn as a substitute for fossil fuels in an effort to mitigate anthropogenic climate change (which supposedly has a negative impact on the production of crops such as corn).

This is about as logical as publicity-stunt burnings of Harry Potter books because of objections to the contents within, which only results in more people buying and reading the books to find out what got the book-burners so inflamed in the first place.

With Harry Potter it was the fantasy world of witchcraft and wizardry. With corn ethanol it is the fantasy world of agriculturally damaging climate change.

A few years ago, a paper was published in the prominent scientific journal Science by Stanford’s David Lobell and colleagues that reported that human-caused global warming over the past 30 years resulted in a slowdown in global crop production. Modeling the climate response of the world’s four largest commodity crops—corn, rice, wheat, and soybeans—Lobell’s team calculated that as a result of rising temperatures and precipitation changes, global crop production was about 3 percent less than it otherwise would have been.

But consider this: The United States produces about 36 percent of the world’s corn. And about 40 percent of U.S. corn is used to produce ethanol for use as a gasoline substitute in an attempt to lower net carbon dioxide emissions from driving and reduce climate change. Globally, corn makes up 30 percent of total worldwide production of the four crops studied by Lobell’s group.

Multiply all these percentages out, and you get that the United States is burning a bit more than 4 percent of global crop production in an attempt to mitigate a climate-driven loss of 3 percent of the global crop production.

How crazy is that, you may ask?

About as crazy as burning witches because of climate change and associated crop failures (a popular pastime* during the Little Ice Age).

To make matters worse, the 3% slowdown in crop production (we use “slowdown” because during the 1980–2008 study period the total production of the four crops examined by Lobell et al. increased by about 75 percent, so global crop production is actually booming in the face of climate change), that calculation does not take into account the fertilization effect for crops of the increase in atmospheric carbon dioxide (from our burning of fossil fuels).

When Lobell et al. made a rough estimate of the benefits of additional carbon dioxide, the slowdown dropped to less than 1 percent.

And even this less-than-1 percent impact was described by Lobell et al. as perhaps being “overly pessimistic” because it did not fully incorporate long-term adaptive farming responses to changing climate conditions (i.e., farmers are not as dumb as statistical models make them out to be).

What this means is that even under overly pessimistic scenarios, we still currently burn more than 4 times as much grain as climate change has taken away. Thinking about this in future terms, if we observe twice as much climate change from 2010 through 2038 as we did from 1980 to 2008 (Lobell’s study period), all we would have to do is stop burning half as much ethanol as we do now to make up for the entire global climate-related crop reduction.

The irrational fear that climate change will lead to global crop failures is risible. Burning crops to alleviate that fear will ultimately condemn the perpetrators to permanent laughingstock status, alongside those fanning the flames under witches, warlocks, and other objectionable words.



Lobell, D.B., W. Schlenker, and J. Costa-Roberts, 2011: Climate trends and global crop production since 1980. Science, 333, 616-620.


* In a 1999 study published in the journal Climatic Change, Wolfgang Behringer had this to say about what he learned from his investigations into witch hunts and climate change during the Little Ice Age (sage advice to keep in mind!):

Despite attempts of containment, such as the calvinistic doctrine of predestination, extended witch-hunts took place at the various peaks of the Little Ice Age because a part of society held the witches directly responsible for the high frequency of climatic anomalies and the impacts thereof. The enormous tensions created in society as a result of the persecution of witches demonstrate how dangerous it is to discuss climatic change under the aspects of morality.