Of Coffee and Climate: Anecdote Replaces Science

Of Coffee and Climate: Anecdote Replaces Science
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“So profound is our ignorance, and so high our presumption, that we marvel when we hear of the extinction of an organic being; and as we do not see the cause, we invoke cataclysms to desolate the world, or invent laws on the duration of the forms of life!”
Charles Darwin, The Origin of Species

Writing more than 150 years ago, Charles Darwin identified the central problem with humanity’s ability to understand nature’s complex interactions. We believe we are intelligent enough to sort out obscure natural processes, so we invent stories that seem to explain what we are seeing. Darwin recognized, however, that we presume too much, failing to see the real causes of events.

The strength of the modern scientific method is its ability to carefully test those stories. That process, however, is often at odds with the storytelling at the center of environmental journalism. A recent story in The Seattle Times about climate change and Costa Rican coffee is an excellent example of how a compelling story can lead reporters to mistake local anecdotes for global scientific data.

Published on March 5, the story’s headline captures the tone: “Climate change takes toll on coffee growers, drinkers too”. The impact of climate change on coffee, they argue, has been significant. “Yields in Costa Rica have dropped dramatically in the last decade,” the Times wrote, “with farmers and scientists blaming climate change for a significant portion of the troubles.”

But there are factual problems with the story.

(1) According to NASA, Costa Rican temperatures during 2008-09, the years with the largest drop in production, were only 0.6 degrees warmer than the 20th century baseline. The most significant increase occurred in the fall (September-November, 2008), of just over 1 degree F. This was left out of the story.

(2) Average temperatures in 2008-09 were only 0.1 degrees warmer than 1998-2000, when Costa Rican coffee harvests were 68 percent larger. The largest difference occurred in the fall, a difference of only 0.7 degrees.

(3) Temperatures in 2008-09 are actually 0.1 degrees lower than the average annual temperature during the 1991-93 period, which marked the country’s highest coffee production.

Climate scientists also say we are not currently seeing impacts. Dr. Mike Wallace, a climate scientist at the University of Washington told me “the warming of the past 10 years is pretty small, both globally and over Costa Rica. I'm not at all sure that it's been a factor in the decline of coffee production on this short time scale.” Ironically, Wallace is the very scientist chosen by The Times to answer climate questions in an online chat they hosted about the article.

So, how did The Times reporters come to believe that climate change was the cause of the decline in the coffee crop? Initially, Melissa Allison, the lead reporter, says she expected to hear about the future, “but instead they [coffee growers] were showing us things we never expected to see now.” One of those was Ronald Peters, director of the Costa Rican national coffee agency who is quoted saying “climate change represents about a quarter of the problem.” How did Peters arrive at this conclusion? Allison explained in an e-mail to us:

With their finite resources, the researchers I read and talked to are working on projections for the future and/or how to solve the problems farmers are having rather than quantifying exactly how much a problem it is. But I wanted to know for this story whether people seeing the problem thought the climate aspect was small, medium or big. I asked everyone and used Peters' response partly because he has a broad understanding of what's happening throughout the country.”

In other words, after being prompted by the reporter, Peters offered a guess. Ultimately, she conceded, “it's impossible to know how much of the situation is due to big changes in the weather.” That sentiment, however, is not reflected in the article’s claim that climate change is already “taking a toll on the lucrative coffee crop.”

Instead of talking to climate scientists, Allison relied on anecdotes. She determined that climate change was a part of the problem because “everyone said that's part of it, and we tried to document their examples.” Substituting the personal memories of coffee growers for recorded data is unscientific.

It is possible that such small changes in temperature have caused the impacts seen in Costa Rica. There are indications that this is unlikely, however.

(1) Coffee plants tolerate a range of temperatures. According to the University of Hawaii, Hawaiian Arabica coffee is grown in a zone from sea level to 2,000 feet, where temperatures vary by about seven degrees. A difference of one half degree would be much smaller than the natural range coffee can tolerate in Hawaii. Shifting the crop by 150 feet of elevation would equal the entire Costa Rican temperature change over the last twenty years. It is unlikely that this small amount of warming has caused the crop decline.

(2) The total worldwide coffee crop in 2009 was nearly twice the level of 1999. Although The Times claims climate change is “helping push up the price of a latte or espresso,” the more likely culprit is rising consumer demand.

(3) The reduction in the Costa Rican coffee crop has been most significant during only the past few years. The most significant drop occurred in 2008, with production falling by more than a quarter. This is significant, but not unprecedented. For example from 1985 to 1986, Costa Rican coffee production fell by half.

So, what is causing Costa Rica’s coffee decline? As the reporter admits, “it’s impossible to know.” Readers of the article, however, would not know that. The consistent message is that climate change is lowering coffee yields in Costa Rica, and driving up the cost of coffee.

The data do not support that conclusion and climate scientists agree.

As Darwin warned, we are susceptible to presuming we understand the cause of natural events even when our ignorance is profound. Science journalism can be especially susceptible, substituting a simple compelling story for the complexity of data-based science. Reporting the uncertainties of scientific information may not result in gripping journalism, but it is critical to enabling the public and policymakers to rely on the stories they read about climate change or the other environmental challenges we face.

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