Document: JAN-3-66-4

Climate change or changing climate variability: Which is worse for crop growth in the midwestern region of the United States?

SOUTHWORTH, J.* ¹, J.C.RANDOLPH ¹, O.C.DOERING ², M.HABECK ², R.A.PFEIFER ² and M.A.MAZZOCCO ³

Indiana University, Bloomington, IN 47405-1701 USA ¹
Purdue University, West Lafayette, IN 47907 USA ²
University of Illinois, Urbana, IL 61801 USA ³

Abstract:
Starting with the assumption of global climate change by 2050 this research concentrates on assessing how agriculture in the Upper Midwest of the US will adapt to such climate change. Climatic variability in the form of temporal fluctuations and spatial variations, is often more important, and may have more impact on crop growth than changes in average values. In this study, climate data for current conditions (VEMAP dataset) and for two future scenarios (HADCM2 model), in the form of monthly and daily values, were used to evaluate crop growth using DSSAT version 3.5, for 2050-59. These same climate data were then manipulated by changing their standard deviations to produce increased or decreased climate variability scenarios. Results were evaluated across 10 different locations, crop types, and climate scenarios (control or current conditions, mean changes, variance changes, mean and variance changes). The changes in climate do produce variable, crop specific results, with southern areas of our study region generally showing decreased yields for maize and soybean, and our northern areas having increasing yields. Differences are quite evident however, concerning the role of changes in the mean versus changes in variability, with increased variability climate scenarios producing dramatic and very damaging crop losses. Decreased variability scenarios however have the opposite effects, with large yield increases being the dominant trend. At atmospheric CO₂ concentrations of 555 ppmv, CO₂ fertilization effects indicate a potential for increased yields, especially for soybeans, with > 20% yield increases under ideal growth conditions. Maize shows a more limited fertilization effect with approximately 5% yield increases when conditions are considered ideal. When plant growth is limited due to other environmental factors, e.g., temperatures, CO₂ fertilization effects are negligible.

Keywords: variability, extremes, threshold temperatures, north-south gradients

This abstract is being presented at: 2:15 PM in session:
Oral Session #66: Large Scale Climate Change.