Right on the heels of a report from the National Oceanic and Atmospheric Administration announcing that the December-February three month stretch was the warmest ever recorded in the United States, comes a paper in Environmental Research Letters declaring that rising temperatures between 1981-2002 depressed global production yields for wheat, corn, and barley. (Thanks to MongaBay for the link.
It's hard to know exactly what to make of this paper: expertise in advanced statistical analysis techniques would be required to begin making a knowledgeable critique. If I understand it correctly, I'm not sure even sure that the paper's authors are stating that yields physically declined, but rather that their numbers indicate how much one would expect yields to fall if farmers did not do anything to compensate for the changing conditions.
Potential impacts of temperature increases may have also been countered by adaptation measures taken by farmers, such as changes in planting dates or use of different cultivars. Any such gradual changes would not have been captured by the statistical models, which utilized detrended data. Thus, the yield impacts of climate trends reported here can be viewed as the expectation in the absence of explicit recognition of, and adaption to, climate trends since 1980 [Italics mine]. The extent to which farmers adapt to climate trends is thus a source of uncertainty in estimating impacts of climate change, as it is for projecting future impacts.
It's unclear to me whether this means that the numbers would be even worse if one was able to figure out how much farmer adaptation had mitigated the damage, or that through some statistical sleight of hand the researchers figured out what should have happened, regardless of what actions were taken by farmers. If the latter, this strikes me as something of a large loophole -- maybe, as some critics of global warming "alarmism" like to predict, we'll soon be farming genetically modified rice in newly balmy subarctic tundra regions. Don't worry: just adapt.
Or maybe not. Maybe this is the kind of paper that should send a chill through everyone paying attention. A world with both surging temperatures and a burgeoning population is a world where agricultural production is put under greater and greater stress. Three of the five warmest years on record came after 2002, note researchers David B. Lobell and Christopher B. Field. This problem isn't going away.
A side note: Environmental Research Letters is an open-access online journal launched in October 2006, a welcome addition to the world of publicly accessible scientific research. It seems that hardly a week goes by where I don't discover another such recently created resource. When combined with the volunteer efforts of people who spend their spare time scanning and digitizing research papers from years gone by (a good example, which I also learned about today, are the newly accessible archives of the Journal of Sino-Japanese studies) the sense conveyed of a constantly expanding online infosphere is exhilarating, and overwhelming. We may have no answers to the problems that afflict us, but we will not lack for data or analysis!