Indo-Pacific Ocean warming increases the uncertainty in forecasting the onset of the South China Sea summer monsoon

The onset of the South China Sea summer monsoon (SCSSM), usually characterized by a simultaneous circulation–convection transition, marks the beginning of the East Asian summer rainy season. Thus, forecasting it at the subseasonal-to-seasonal scale is a key concern. On the basis of previous findings, the El Niño–Southern Oscillation (ENSO) signal in winter is regarded as the most important predictor for SCSSM onset. Furthermore, research shows that western Pacific warming has advanced the SCSSM onset time since 1994.