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Heat waves—prolonged periods of abnormally hot weather—influence egg prices, energy bills and even public transit. And they're becoming more common as temperatures increase.

In a new study published in Communications Earth & Environment, UIC researchers report that heat waves across Africa are today than 40 years ago, mainly due to increased greenhouse gas and black carbon emissions from burning fossil fuels. Understanding heat waves' origins and effects can help African countries predict them and adapt.

"Raising awareness of heat waves is critical to saving human life," said Akintomide Afolayan Akinsanola, head of the Climate Research Lab and assistant professor of Earth and environmental sciences in the UIC College of Liberal Arts and Sciences. "In a developing continent like Africa, where the capacity for adaptive infrastructure is relatively low, heat waves can have greater consequences."

Africa is uniquely vulnerable to heat waves in an already warming world; in April 2024, temperatures in the West African city of Kayes . Heat waves harm ecosystems, reduce agricultural productivity and strain energy systems. Infants, older adults and those with health conditions are especially susceptible to heat-related illness, which kills 5,600 people annually in the U.S. Some experts have estimated that heat-related deaths in Nigeria may rise to 23,000 or even 43,000 per year by the end of the 21st century.

But climate extremes in Africa and its subregions are understudied due to insufficient computing infrastructure and a lack of data and resources, the researchers said. Filling this knowledge gap could protect people living in these regions and help forecast similar scenarios around the globe.

Akinsanola and his team examined the intensity, frequency and duration of heat waves in Africa during two periods: 1950–1979 and 1985–2014. The researchers used large–ensemble computer models to isolate the factors contributing to daytime, nighttime and compound heat waves, including human-driven influences like greenhouse gas and aerosol emissions as well as natural variability.

The researchers saw stark differences between the two periods they studied. The 1950–1979 period was characterized by weak, infrequent heat waves, with about one occurring every three to eight years. About 80% of heat wave activity during this time could be attributed to natural causes, and the researchers highlighted the cooling effects of sulfate aerosol: airborne sulfur particles caused naturally by volcanic eruptions or anthropogenically through fossil fuel burning make clouds reflect more light back into space.

In contrast, the 1985–2014 period saw one or more heat waves every two years, lasting up to three times as long as in the previous period. These changes were mainly due to human activities like increased greenhouse gas and black carbon emissions. In this period, the researchers attributed only 30% of heat wave activity to natural causes.

The team also identified a strong correlation between heat wave frequency and near-surface air temperature, likely due to shared variables like air circulation and surface energy.

"I was surprised to see that these changes were consistent across the African subregions, not just a specific isolated area," said Vishal Bobde, a doctoral student in Akinsanola's lab and the study's first author.

The authors hope their findings will help policymakers, scientists, government officials and African communities develop effective mitigation and adaptation strategies for heat waves, such as strengthening early-warning systems and improving heat-risk literacy.

"The impacts are wide-ranging, from productivity to food shortage to energy," said Akinsanola, who is jointly appointed at the Environmental Science Division of Argonne National Laboratory. "Remember that the African population is close to 2 billion. Heat waves can lead to drought, trigger migration and spark conflicts, thereby impacting regional, continental and even global stability."

Looking ahead, the researchers plan to investigate how projections for future heat waves might change based on global adherence to the goals set in the .

"While Africa contributes a relatively small share of global greenhouse gas emissions, climate change is a global issue that is intensifying heat waves everywhere. Addressing this requires global cooperation to aggressively reduce emissions and build adaptive capacity," said Kayode Ayegbusi, co-first author and UIC doctoral student in Akinsanola's lab.

Institutional collaborators include The Australian National University, Texas A&M and the University of California, Merced. The researchers used Community Earth System Model 2—Large Ensemble simulations, which are managed by the National Center for Atmospheric Research and are through the Earth System Grid Federation or NCAR Climate Data Gateway.