The Indo-Pacific warm pool (IPWP) is crucial for regional and global climates. However, the development of the IPWP and its effect on the regional climate during the Cenozoic remain unclear. Here, using a compilation of SST records and multimodel paleoclimate simulations, we show that the extent, intensity and warmest temperature position of the IPWP changed markedly during the Cenozoic. Specifically, its extent decreased, its intensity weakened, and its warmest temperature position shifted from the Indian to the western Pacific Ocean over time. The atmospheric CO₂ dominated its extent and intensity changes, while paleogeography, by restricting the distribution of the Indian Ocean and the width of the tropical seaways, controlled the shifts in its warmest temperature position. In particular, the eastward shift in the warmest temperature position to the western Pacific Ocean from the middle to late Miocene inferred from compiled SST records likely resulted from the constriction of tropical seaways. Furthermore, by changing the atmospheric thermal structure and atmospheric circulation, the reduced extent and intensity of the IPWP decreased the annual precipitation in the western Indian Ocean, eastern Asia and Australia, while the shift in the warmest temperature position from the Indian to western Pacific Ocean promoted aridification in Australia. These findings imply that, from the perspective of past warm climates with high concentrations of atmospheric CO₂, the expansion and strengthening of the IPWP will occur in a warmer future and favor excessive precipitation in eastern Asia and Australia.

warm pool,Cenozoic,paleogeography,atmospheric co2