The Amazon basin experienced a prolonged drought in the 2010s, impacting ecosystems and society. This study uses large ensemble simulations to determine if this was due to external forcing or internal variability, and whether it will continue. Results show a negative-to-positive phase transition of the Interdecadal Pacific Oscillation (IPO) explains ~45% of the observed decadal drought, significantly more than external forcing (~12%). Constraining future IPO phase transition reduces uncertainty in near-term (pre-2040) Amazon rainfall projection. The IPO plays a crucial role in the post-2010 drying and near-term rainfall projection.

Yi Liu, Wenju Cai, Yu Zhang, Xiaopei Lin, Ziguang Li