Many of my students labor under the misconception that climate change impacts are not currently being manifested. An excellent new study in Science, Lobell, et al., Climate Trends and Global Crop Production Since 1980, 333 Science 616-20 (2011) once again demonstrates the contemporaneous fingerprints of climatic change, but also demonstrates the large uncertainties in seeking to establish the precise nature and extent of this fingerprint. Among the take-aways of the article:

1. Global average temperatures have been increasing by 0.13C since 1950. Temperatures are anticipated to increase at a faster clip of 0.2C  per decade over the next 2-3 decades, with even greater increases in land areas where crops are cultivated
2. Time series of average growing-season in the study revealed significant positive trends in temperature since 1980 for nearly all major growing regions of maize, wheat, rice, and soybeans; one notable exception was the United States, which accounts for 40% of corn and soybean production, and where temperatures have actually dipped slightly;
3. Based upon the yield response utilized in this study, the researchers concluded that maize and wheat exhibited negative impacts for several major producers and global net loss of 3.8% and 5.5%, respectively, relative to what would have been achieved without the climate trends in 1980–2008. The most notable decline was a 15% decrease in wheat production in Russia. By contrast, the net impact on rice and soybean production was insignificant;
4. Changes in temperature, rather than precipitation have been, and are likely to continue, to have more impact on crop production;
5. Climate impacts often exceed 10% of the rate of yield change, indicating that “climate changes are already exerting a considerable drag on yield growth.” The study also indicated that climate change is also responsible for substantial increases in commodity prices. Overall, the authors concluded that “climate change is likely incurring large economic and health costs.”

Related posts:

1. The Impact of Climate Geoengineering on Crop Yields
2. Ocean Iron Fertilization and Potential Toxic Diatom Production
3. Impacts of Biofuel Production