Climate Study Reveals Alarming Trends in Heat Wave Dynamics

Forces that drive climate change do more than just create warming temperatures; they cause more frequent extreme weather events, including heat waves. The global impact of heat waves is one reason that stories about the research have appeared in more than 600 media outlets worldwide.

A study recently published in the journal Science Advances by an international team of scientists, including Utah State University climate scientist Wei Zhang, found worrisome trends indicating that from 1979 to 2020, heat waves globally became more frequent, persisted longer, covered larger areas, and brought increasingly hotter temperatures.

The scientists found that during those four decades, periods of consecutive hot days that constitute a heat wave happened more often and the atmospheric patterns that create them moved more slowly — nearly 5 miles per day slower each decade — meaning heat waves are longer lasting and creating more problems. The researchers found an average of 98 heat waves per year between 2016 and 2020, a substantial increase compared to the average of 75 per year from 1979 to 1983.

Other studies have shown that heat waves are worsening. This newly published work is more comprehensive and includes a look at their duration and how they travel, forming large contiguous heat waves that travel across continents.

“The contiguous heat waves have serious impacts on human health and infrastructure like roads and power grids,” Zhang said. “They impact the environment because heat waves can influence droughts, wildfires, and air pollution, which are familiar environmental problems we are facing.”

Heat waves have also become longer lasting. From 1979 to 1983, heat waves lasted an average of eight days. However, from 2016 to 2020, they lasted an average of 12 days.

To analyze the mechanisms behind more extreme heat waves, the researchers used decades of weather and climate data to conduct computer simulations that showed the relatively rapid change can be attributed to human-caused increases in greenhouse gas emissions. They conducted global computer simulations that removed the effects of burning coal, oil, and natural gas and concluded that natural climate variability alone could not produce the same results.

The misery of longer, stronger heat waves is not evenly distributed around the world and they tend to travel farther in South America, but last longer in North America and Eurasia.

The global impact of heat waves is one reason that stories about the research have appeared in more than 600 media outlets worldwide. To read or hear more about the study and Zhang’s comments on it, see The New York Times story or reporting by the Associated Press.

Other Climate Research Close to Home

Zhang is also part of a research effort close to home that is supported by the National Oceanic and Atmospheric Administration (NOAA). Salt Lake City is among the cities NOAA selected to study the impacts of urban heat islands and work toward mitigating their effects.

Heat is retained and amplified in cities because there is typically an abundance of asphalt and other dark surfaces, little vegetation, and buildings that interfere with air circulation. In Salt Lake City, Zhang and Daniella Hirschfeld, a USU assistant professor whose work focuses on climate adaptation planning and urban ecology, work with volunteers (including some young scientists at Rowland Hall School) to record temperatures in many locations across the city. The resulting hyperlocal heat map of the city will help guide work to plant more trees in certain spots and take other actions that can help create cooler conditions.