Thermal threshold

Credit: © ISTOCKPHOTO.COM / GEORGE BURBA

Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0906865106 (2009)

Crop yields in the United States — the world's largest exporter of agricultural products — could fall as much as 82 per cent by 2100 if temperatures rise sharply, according to a new study.

Wolfram Schlenker of Columbia University, New York, and Michael Roberts of North Carolina State University in Raleigh examined the effects of growing-season temperatures on corn, soybean and cotton yields in the US using agricultural records and detailed weather data collected between 1950 and 2005. They found a nonlinear relationship between temperature and productivity: yields increased modestly until a threshold temperature was reached at 29 °C for corn, 30 °C for soybean or 32 °C for cotton, after which they declined. This was true for all regions of the US, including the warmer southern states. Using a global climate model, Schlenker and Roberts found that if temperatures rise slowly, yields could fall 30 to 46 per cent by 2100, but that the drop could be as much as 82 per cent under a rapid warming scenario.

The study, however, did not account for gains in productivity caused by elevated CO2 concentrations, which may at least partially offset any decline in yield due to warming.

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Armstrong, A. Thermal threshold. Nature Clim Change 1, 110 (2009). https://doi.org/10.1038/climate.2009.88

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