Climatologists have been working for years to understand and numerically represent these complex chains of interacting events in climate models – a daunting task that pushes the limits of available computing power. “It’s only been in the last five years or so that a framework has been developed to apply compound risk thinking to climate analysis in a way that you can actually calculate without putting yourself desperately over the top. out of your head,” said the study’s lead author, Colin Raymond, a scientist at NASA’s Jet Propulsion Laboratory in Southern California.
For their study, the research team used a well-known German climate model called the Max Planck Institute Grand Ensemble to run 100 individual simulations from the years 1991 to 2100. Simulations from the past (1991 to 2020) showed that the model was able to represent clusters of extreme events, such as weathering extreme heat with extreme precipitation, in accordance with how they actually occurred during that time. The researchers analyzed simulations of the future up to 2100 to examine likely future changes in climate hazards, particularly hazards that could occur simultaneously or in close succession.
Raymond and his colleagues focused on how the increased clustering of temperature and precipitation risk will affect corn. This important food crop is grown worldwide, with six major regions, or granaries, accounting for about two-thirds of all production. The United States is the world’s largest corn producer, harvesting some 419 million tonnes (380.3 million metric tons) in 2021.
Model simulations showed that by 2100, extreme heat waves around the world lasting at least three days will occur two to four times more often than today. Extreme three-day rainfall events will typically increase by 10-50% in frequency. The researchers also analyzed how these heightened events will cluster in time and space. They then looked at how all of these changes combined could affect future maize harvests, using as a guide the relationship between climatic extremes in heat and rainfall and past crop failures.
According to their best estimate, the probability that a cluster of events will cause maize crops to fail in at least three of the world’s granaries in the same year will almost double, from 29% to 57%, by the year 2100. Although low, the likelihood of crops failing in the five largest breadbasket regions in a single year will increase even more significantly – from 0.6% to 5.4%. The US Midwest is the region most likely to be included in years with three breadboard failures, followed by Central Europe.
The study also looked at how the risks to wildfires and human health would increase as the extremes follow each other more closely. All of the results showed, Raymond said, that “things are interconnected in a way that we haven’t quite appreciated until now. It’s not just heat waves. It’s not just the heat and the drought. It is all of these interconnections that best explain the severe impacts that concern us most when trying to prevent major disasters.