Urban population exposure to apparent temperature whiplash is projected to increase with global warming

Apparent temperature whiplash, characterized by abrupt transitions between hot and cold perceived temperature, poses a great threat to urban climate adaptation. Effective risk assessment requires a comprehensive, human-centered framework to quantify this phenomenon. Here we assess historical and projected global patterns of apparent temperature whiplash, their drivers, and associated risks using an ensemble of reanalysis datasets and climate model projections across multiple scenarios. We show that from 1940 to 2022, urban areas worldwide experienced an annual mean of 401 ± 43 events, while the exposed population rose from 630 million to more than 2.4 billion. We attribute most of this increase to anthropogenic forcings. Projections indicate increases in event frequency, affected area, and exposed population, particularly under higher-emissions scenarios. Our findings quantify the risks of these abrupt transitions and provide crucial guidance for policymakers to enhance early warning systems and develop strategic adaptation measures. Over the past 80 years, urban areas have experienced more apparent-temperature whiplash events, and projections suggest that their frequency, along with the affected population, will continue to grow, especially under higher-emission scenarios, according to climate models and observations.