PNNL

Abstract

Solar radiation management could affect agriculture productivity due to changes in temperature, precipitation and solar radiation. To study rice and maize production changes in China, we used results from 10 climate models participating in the Geoengineering Model Intercomparison Project (GeoMIP) G2 scenario to force the Decision Support System for Agrotechnology Transfer (DSSAT) crop model. G2 assume a 50-year period of solar reduction to balance a 1% per year increase of CO2, or 1pctCO2, followed by 20 years of unmodified insolation. We first evaluated the DSSAT model using 30 years (1978-2007) of daily observed weather records and agriculture practices for 24 major agriculture provinces in China, and compared the results to observations of yield. We then created three sets of climate forcing for 41 locations in China for DSSAT from each climate model: (1) 1pctCO2, (2) G2, and (3) G2 with constant CO2 concentration (409 ppm), and compared the resulting agricultural responses. Without changing management practices, the combined effect of climate changes due to geoengineering and CO2 fertilization during the last five years of solar reduction would change rice production in China by -4.6±6.0 Mt (4.5±5.9%) as compared with 1pctCO2 and increase Chinese maize production by 20.9±6.9 Mt (14.8±4.9%). The termination of geoengineering shows negligible impacts on rice production but an 8% reduction of maize production as compared to the last five years of geoengineering. The CO2 fertilization effect compensates for the deleterious impacts of changes in temperature, precipitation and solar radiation due to geoengineering on rice production, raising rice production by 8.2 Mt. The elevated CO2 concentration enhances maize production in G2, contributing 35.5% to the total increase. While the climate changes from stratospheric geoengineering would have small negative impacts on rice production in China, it would significantly increase maize production.