Early warning signals for Asian summer monsoon tipping and implications for future monsoon changes

As shown by paleoclimate data and climate models, many climate systems on Earth undergo abrupt shifts when they cross tipping points (TPs), and these abrupt shifts are sometimes preceded by early warning signals (EWS). As a vital component of Earth's climate system, the Asian Summer Monsoon (ASM) system sustains the survival of billions of people. However, it remains unclear whether paleo-ASM abrupt events were preceded by EWS and whether the abrupt shifts in the ASM may ensue in the near future. In this study, we identified EWS preceding abrupt shifts in the ASM circulation using high-resolution speleothem δ18O records, including rising variance and autocorrelation, and weakening resilience. Our analyses reveal akin EWS both in periods preceding historical ASM abrupt events (e.g., Heinrich events) and in modern records over the last 200 years, suggesting a plausibility that the ASM is approaching a TP by the mid-21st century. The dynamic coupling of the ASM circulation with the Atlantic meridional overturning circulation provides a possible mechanism behind the persistent reoccurrence of abrupt ASM transitions. These findings position the ASM system as a potential climate tipping element, and the potential tipping of its circulation can profoundly change spatiotemporal rainfall patterns over the ASM domain, thus necessitating urgent research.