Crop-climate feedbacks boost U.S. maize and soy yields

Keywords: climate change, agriculture
Session Type: Virtual Paper
Day: Wednesday
Session Start / End Time: 4/7/2021 08:00 AM (Pacific Time (US & Canada)) - 4/7/2021 09:15 AM (Pacific Time (US & Canada))
Room: Virtual 46

Abstract

Crop yields have grown rapidly over global breadbaskets since 1960. Higher yields mean that crops produce more evapotranspiration (ET), pumping water into the lower atmosphere and modifying the surface energy balance. In some high yielding regions like the central U.S., maximum temperatures have cooled over the past four decades despite rising greenhouse gas concentrations, an effect which has benefited yields. We show that this cooling has been driven by crop ET growth raising the evaporative fraction, increasing latent heating and reducing sensible heating during the growing season. This crop-driven cooling results in a positive feedback that we call the crop-climate feedback: crop yield growth modifies the local climate in a way that benefits crops and promotes further yield growth. In some regions, the feedback can account for nearly 15% of maize yield growth since 1980, and across the U.S., we find that the feedback has entirely balanced out the detrimental effects of warming over that time period. Here we analyze how the crop-climate feedback modifies the surface energy balance, assess the feedback’s strength and variability, and project how it may evolve as greenhouse gas forcing increases and yield growth potentially slows in the coming decades.