Very Hot and Very Dry Conditions Have Doubled Worldwide Posing Serious Threat to Food Systems, Study Finds

Stanford University and Charles III University   Yale Environment 360 Summary

The chance of having years that are both extremely warm and extremely dry — conditions that pose a serious threat to agricultural systems — has doubled around the globe since 1931, according to a new study published in the journal Science Advances. The research attributes this change almost entirely to human-driven climate change.

The study, conducted by scientists at Stanford University and Charles III University of Madrid, also found an uptick in dry and severely warm conditions in multiple key agricultural regions in the same year, which reduces the possibility that surpluses in one location can make up for low yields in another.

“When we look in the historical data at the key crop and pasture regions, we find that before anthropogenic climate change, there were very low odds that any two regions would experience those really severe conditions simultaneously,” Stanford climate scientist Noah Diffenbaugh, lead author of the new study, said in a statement. “The global marketplace provides a hedge against localized extremes, but we’re already seeing an erosion of that climate buffer as extremes have increased in response to global warming.”

The California drought is devastating agriculture across the state. Credit: Cerabona/Flickr

Diffenbaugh and his colleagues also found that the frequency of these simultaneous hot-dry conditions will continue to increase, by about 20 percent, over the next three decades if nations don’t drastically reduce their greenhouse gas emissions, E&E News reported.

Ali Sarhadi, María Concepción Ausín, Michael P. Wiper, Danielle Touma1 and Noah S. Diffenbaugh. Multidimensional risk in a nonstationary climate: Joint probability of increasingly severe warm and dry conditions. Science Advances  28 Nov 2018:
Vol. 4, no. 11, eaau3487 DOI: 10.1126/sciadv.aau3487

Abstract

We present a framework for quantifying the spatial and temporal co-occurrence of climate stresses in a nonstationary climate. We find that, globally, anthropogenic climate forcing has doubled the joint probability of years that are both warm and dry in the same location (relative to the 1961–1990 baseline). In addition, the joint probability that key crop and pasture regions simultaneously experience severely warm conditions in conjunction with dry years has also increased, including high statistical confidence that human influence has increased the probability of previously unprecedented co-occurring combinations. Further, we find that ambitious emissions mitigation, such as that in the United Nations Paris Agreement, substantially curbs increases in the probability that extremely hot years co-occur with low precipitation simultaneously in multiple regions. Our methodology can be applied to other climate variables, providing critical insight for a number of sectors that are accustomed to deploying resources based on historical probabilities.