Contrasting impacts of dry versus humid heat on US corn and soybean yields

Abstract

The impact of extreme heat on crop yields is an increasingly pressing issue given anthropogenic climate warming. However, some of the physical mechanisms involved in these impacts remain unclear, impeding adaptation-relevant insight and reliable projections of future climate impacts on crops. Here, using a multiple regression model based on observational data, we show that while extreme dry heat steeply reduced U.S. corn and soy yields, humid heat extremes had insignificant impacts and even boosted yields in some areas, despite having comparably high dry-bulb temperatures as their dry heat counterparts. This result suggests that conflating dry and humid heat extremes may lead to underestimated crop yield sensitivities to extreme dry heat. Rainfall tends to precede humid but not dry heat extremes, suggesting that multivariate weather sequences play a role in these crop responses. Our results provide evidence that extreme heat in recent years primarily affected yields by inducing moisture stress, and that the conflation of humid and dry heat extremes may lead to inaccuracy in projecting crop yield responses to warming and changing humidity.

Subseasonal Variability of Humid Heat During the South Asian Summer Monsoon

“…While Tdry tends to peak during the pre-monsoon season throughout the region (van Oldenborgh et al, 2018), recent work has suggested that the highest humid heat magnitudes often occur after monsoon onset in parts of South Asia (Raymond et al, 2020;Rogers et al, 2021). Differentiating between dry and humid heat extremes in this region is particularly important given their distinct impacts on plant and human health, respectively, which can both be detrimental to agricultural production (Diaz et al, 2023;Ting et al, 2023). Ivanovich et al (2022) highlighted that elevated Tw during the June-August season in India is associated with surface level easterly wind anomalies and increased dry bulb temperature and specific humidity, conditions sometimes associated with monsoon breaks.…”