Rapid flips between warm and cold extremes in a warming world.

Rapid temperature flips are sudden shifts from extreme warm to cold or vice versa-both challenge humans and ecosystems by leaving a very short time to mitigate two contrasting extremes, but are yet to be understood. Here, we provide a global assessment of rapid temperature flips from 1961 to 2100. Warm-to-cold flips favorably follow wetter and cloudier conditions, while cold-to-warm flips exhibit an opposite feature. Of the global areas defined by the Intergovernmental Panel on Climate Change, over 60% have experienced more frequent, intense, and rapid flips since 1961, and this trend will expand to most areas in the future. During 2071-2100 under SSP5-8.5, we detect increases of 6.73-8.03% in flip frequency (relative to 1961-1990), 7.16-7.32% increases in intensity, and 2.47-3.24% decreases in transition duration. Global population exposure will increase over onefold, which is exacerbated in low-income countries (4.08-6.49 times above the global average). Our findings underscore the urgency to understand and mitigate the accelerating hazard flips under global warming.