by Adin Bonapart
Rosenzweig et al. (2014) perform an intercomparison of seven global gridded crop models (GGCMs) and analyze their combined effectiveness in predicting the outcomes of climate change on the world’s food systems. Differences in the structure, purpose, and process between individual models are major sources of uncertainty in multi-model climate change assessments. Regardless of their high degrees of uncertainty however, global crop projections indicate substantial crop-yield losses worldwide, particularly in the tropics.
Although climate change will affect agriculture globally, the strongest effects are going to be felt in the lower latitudes where developing countries are concentrated. Even moderate (1−2 °C) rises in temperatures will cause significant reductions in agricultural yields in tropical regions, which receive maximal solar energy. Elevated atmospheric temperatures will result in increased evapotranspiration and water demand for crops in these regions, where many important cereal crops are already at or near their upper temperature thresholds.
Nitrogen concentration is another key determinant in the effects of changing climate on crop yields because it limits the photosynthetic enhancement effects from elevated CO2 levels. Simulations that account for nitrogen stress levels show dramatic effects, resulting in over 50% loss of yield in some tropical regions for maize, wheat, rice, and soy, the world’s four top agricultural products.
Rosenzweig, C., Elliott, J., Deryng, D., Ruane, A., et al. (2014). Assessing agricultural risks of climate change in the 21st century in a global gridded crop model intercomparison. Proceedings of the National Academy of Sciences of the United States of America, 111(9), 3268-3273.