Century-scale attribution of winter extreme cold events in the East Asian monsoon region

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Abstract Previous attribution studies have investigated the anthropogenic influence on recent individual extreme cold events. Yet, a century‐scale comparison of anthropogenic influences on the probability of high‐impact extreme cold events across different historical periods remains lacking, as does an assessment of the circulation‐mediated effect via the Siberian High (SH). Here we provide a century‐scale (1901–2024) attribution analysis for the East Asian winter monsoon region, using winter mean temperature and cold‐night indices within a state-of-the-art event attribution framework that explicitly considers the SH as a key circulation system. We find pronounced warming trends emerging since the late 20th century, which are well reproduced by multi‐model ensemble simulations. Event attribution reveals a clear temporal evolution. In the mid‐to‐late 20th century, greenhouse gases (GHG) reduce the probability of extreme cold events, while aerosols simultaneously increase it, with their opposing effects largely canceling each other out—resulting in a negligible net anthropogenic influence. In the 21st century, however, the probability‐decreasing effect of GHG strengthens rapidly and overwhelms the aerosol effect, leading to a marked net reduction in event probability. Annual running risk ratios further confirm that this net anthropogenic influence emerges only in the 21st century. Crucially, the circulation‐mediated effect via externally forced changes in SH intensity or spatial pattern is negligible and has not changed significantly since the early 20th century. These findings provide clear century‐scale evidence that anthropogenic forcings drive temporal variations in extreme cold event probability over this region, with externally forced changes in the SH contributing negligibly to the long‐term change in event probability.

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