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What are the odds that extreme weather will lead to a global food shock? » Yale Climate Connections


Envision, for a moment, a multiyear period of extreme weather, including heat waves, freezes, droughts, floods, and windstorms, topped off by extreme weather during an El Niño event, leading to major crop failures in the U.S.

A disruption of the global agricultural and food supply chain results, leading to panic buying and price shocks. Water shortages cause significant social disruption as populations vie for limited vital resources. The number of countries able to maintain a sustainable level of output shrinks dramatically, the global economy contracts at an accelerating pace, and political tensions rise as countries look to maintain food security. Trade disputes, increased competition and inequality, social unrest, and crime increase, causing widespread business interruption, falling profits, and layoffs, primarily in the agricultural and agriculture-dependent industries.

A 2023 report by insurance giant Lloyd’s explores the odds of such a scenario, using weather data from the past 40 years and a crop model combined with a water-stress model to measure the economic impact of a sustained period of extreme weather.

The report looked at “major,” “severe,” and “extreme” scenarios. The authors found that the “major” case would cost the world $3 trillion over a five-year period, which they estimated has a 2.3% chance of happening per year. Over a 30-year period, those odds equate to about a 50% probability of occurrence — assuming the risks are not increasing each year, which they are.

The costs get even more eye-popping for Lloyd’s “severe” case: $5.7 trillion over a five-year period. This case was estimated to have a 1.1% chance probability of occurrence per year, or a 28% chance over 30 years.

Extreme weather leading to food and water shock’ scenario from Lloyd's
Figure 1. The 2023 ‘Extreme weather leading to food and water shock’ scenario from Lloyd’s. (Image credit: modified from https://www.lloyds.com/news-and-insights/futureset/futureset-insights/systemic-risk-scenarios/extreme-weather-leading-to-food-and-water-shortage/economic-impact)

The “extreme” case, which would cause global havoc, was estimated to cause $17.6 trillion in damage over a five-year period, with a 0.3% probability of occurrence per year — a 9% chance over 30 years. This extreme case would meet the United Nations’s definition of a global catastrophic risk event: a catastrophe global in impact that kills over 10 million people or causes over $10 trillion (2022 USD) in damage.

Why is the food system vulnerable to climate change?

global map showing heat waves hitting five regions simultaneously
Figure 2. Departure of surface temperature from average for the week commencing July 18, 2022, with red indicating higher temperatures. The five circled regions are places experiencing higher-than-normal temperatures concurrently, due to meanders in the jet stream. (Image credit: UK Met Office)

Drought is the great enemy of human civilization, for it deprives us of the two essentials of life — food and water. When the rains stop and the soil dries up, cities can die and civilizations collapse, as people abandon lands no longer able to sustain them. Drought has been identified as the primary or significant contributing factor in the collapse of a surprising number of great civilizations in the past. As I wrote recently in a two-part series on climate change and agriculture, increased drought and extreme heat adversely affecting agriculture likely pose the highest threat to civilization over the next 40 years, as droughts increase in duration, areal coverage, and intensity.

Extreme droughts can affect multiple grain-growing areas simultaneously, causing “food shock” events that could trigger food-price spikes leading to mass starvation, war, and a severe global economic recession. Human-caused climate change is hiking the risk of such simultaneous droughts and their associated heat waves, which have seen a steady increase in recent years because of climate change (Figure 3).

And the odds of a globally disruptive extreme food shock event are steadily increasing as humans burn fossil fuels and pump more heat-trapping climate pollutants into the air.

chart showing increasing heat wave frequency between 1980 and 2020
Figure 3. Top: Frequency of concurrent heat wave days (blue line), and the mean number of heat waves per heat wave day in the May-June-July-August-September (MJJAS) season (orange line) from 1979-2019. Heat wave days are defined as the number of days per MJJAS season with one or more heat wave. Concurrent heat wave days are defined as the number of days per MJJAS season with two or more heat waves. Bottom: change in the number of concurrent heat wave days per decade. Areas with no statistically significant change are stippled with gray dots. (Image credit: Dr. Cass Rogers)

High uncertainty reigns

Modeling of the sort done in the Lloyd’s scenario is subject to high uncertainties because it is attempting to model human behavior and the unprecedented weather extremes climate change is sure to bring. The odds of the various scenarios Lloyd’s has modeled are likely to increase substantially in probability in the coming years, though, because of an increase in climate-change-induced extreme weather.

For example, simultaneous droughts, where multiple grain-producing areas might be adversely affected, are expected to increase by 40% by 2050, according to a 2022 paper in the prestigious journal Nature Climate Change, “Enhanced risk of concurrent regional droughts with increased ENSO variability and warming.” 

A 2019 modeling study, “Concurrent 2018 Hot Extremes Across Northern Hemisphere Due to Human-Induced Climate Change,” found that the area affected by the simultaneous heat extremes expands by about 16% per degree Celsius of global warming. In addition, high heat tends to reduce grain yields — though continued improvements in agricultural technology may help offset this problem.

In a companion explainer published by Carbon Brief on his 2023 paper, “Risks of synchronized low yields are underestimated in climate and crop model projections,” climate scientist Kai Kornhuber warned that climate models can struggle to capture extreme weather events — in particular, those associated with extreme meanders in the jet stream (see an example of such a situation in Figure 2). He wrote, “models may underestimate the potential impact of concurrent extreme weather events on regional crop yields and the consequences of their synchronized failure.”

Number of undernourished people globally, 2005-2022
Figure 4. The number of undernourished people globally fell significantly from the 1970s to around 2010 because of the Green Revolution. These numbers leveled out in the 2010s, but according to the United Nations Food and Agriculture Organization, then began growing, partly because of climate shocks. The COVID-19 pandemic caused an additional increase in 2020-2021. In 2022, the number of undernourished people remained about constant at 735 million, and the percentage of those undernourished was about 9.2%, according to the U.N. (Image credit: FAO)

COVID, inflation, and war have left us vulnerable to a serious food system shock

Inflation-adjusted global food prices, 1961-2023
Figure 5. Inflation adjusted global food prices, 1961-2023. Food prices were record-high in 2022, but declined some in 2023. (Image credit: modified from UN Food and Agricultural Organization)

Given the unprecedented surge in global temperatures over the past year, combined with ongoing disruptions to the food system from the COVID-19 pandemic and the war in Ukraine, the odds of a Lloyd’s food-shock scenario will be higher than usual in 2024.

In addition, the odds of simultaneous droughts hitting major grain-producing regions are higher during El Niño years, such as the one we are currently experiencing — though El Niño is expected to wane by summer, according to the latest outlook from NOAA. Historically, about 46% of concurrent droughts occur during El Niño events, and 22% occur during La Niña events.

Inflation-adjusted food prices during 2023 were down from their all-time high year of 2022, (Figure 5), but are still near record levels, making the global food system more vulnerable than usual to extreme weather shocks. In addition, the number of people experiencing food insecurity is also very high (Figure 4). According to the FAO, 22 nations or territories are expected to see deteriorating food security issues early this year, with famine a risk in Burkina Faso, Mali, Sudan, South Sudan, and Palestine. Conflict is the primary driver of food insecurity in these nations. Concerning global food security in 2024, the FAO report warned:

“Although international food prices are generally declining, they remain high by historic standards, and are expected to come under increased upward pressure in the coming months due to oil price dynamics and the impact of El Niño conditions on agricultural production. In many low- and middle-income countries, persistent elevated commodity prices, weak currencies and depleted foreign-exchange reserves hamper the capacity to import goods of first necessity. Coupled with delays in price transmission and supply chain bottlenecks, these dynamics are contributing to a sharp rise in domestic food prices in several hotspots. Limited economic access is likely to be further compounded by the overall reduction in donor support to offset global hunger.”

Related: My four-part series from 2022

Recklessness defined: breaking 6 of 9 planetary boundaries of safety
The future of global catastrophic risk events from climate change
Food supply and security concerns mount as impacts stress agriculture
Ag’s challenging future in a changing climate

Bob Henson contributed to this post.

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