Solar Irradiance Modulates the Asian Summer Monsoon—ENSO Relationship Over the Last Millennium

The Asian summer monsoon (ASM) is teleconnected to the El Niño Southern Oscillation (ENSO), but this relationship is nonstationary and has shifted significantly in recent decades. Characterizing the drivers of such shifts is crucial for improving ASM prediction and extreme event preparedness. Paleoclimate records indicate a link between ASM strength and solar activity on multidecadal-to-centennial timescales, but 20th-century data are too short to test mechanisms. Here we evaluate how solar irradiance influences the ASM-ENSO relationship using last-millennium paleoclimate data assimilation reconstructions and model simulations. We find that high solar irradiance weakens the ENSO-East Asian summer monsoon (EASM) correlation, but strengthens the ENSO-South Asian summer monsoon (SASM) correlation. Solar irradiance likely influences the strength of the ENSO-EASM and ENSO-SASM teleconnections via changes in the Western Pacific Subtropical High and the amplitude of ENSO events, respectively. We suggest a need for considering solar activity in decadal ASM rainfall predictions under global warming scenarios.