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The Biophysical and Economic Geographies of Global Climate Impacts on Agriculture -- by Uris Baldos, Thomas Hertel, Frances Moore

This paper explores the interplay between the biophysical and economic geographies of climate change impacts on agriculture. It does so by bridging the extensive literature on climate impacts on yields and physical productivity in global crop production, with the literature on the economic geography of climate change impacts. Unlike previous work in this area, instead of using a specific crop model or set of models, we instead employ a statistical meta-analysis which encompasses all studies available to the IPCC-AR5 report. This comprehensive approach to the assessment of the biophysical impacts of climate change has the added advantage of permitting us to isolate specific elements of the biophysical geography of climate impacts, such as the role of initial temperature, and differential patterns of warming across the globe. We combine these climate impact estimates with the GTAP model of global trade in order to estimate the national welfare changes which are decomposed into three components: the direct (biophysical impact) contribution to welfare, the terms of trade effect, and the allocative efficiency effect. We find that the terms of trade interact in a significant way with the biophysical geography of climate impacts. Specifically, when we remove the biophysical geography, the terms of trade impacts are greatly diminished. And when we allow the biophysical impacts to vary across the empirically-estimated uncertainty range, taken from the meta-analysis, we find that the welfare consequences are highly asymmetric, with much larger losses at the low end of the yield distribution than gains at the high end. Furthermore, by drawing on the estimated statistical distribution of trade elasticities, we are also able to explore the interplay between economic and biophysical uncertainties. Here, we find that regional welfare is most sensitive to extremely adverse yield outcomes in the presence of uncertainty in trade elasticities.