New research has traced the deep climatic roots of Asia’s summer monsoon, revealing that the uplift of the Tibetan Plateau was a central driver in transforming the system into one of the world’s most powerful climate phenomena, according to phys.org. In a study published in npj Climate and Atmospheric Science, an international team led by Monash University combined advanced climate modelling with geological evidence to reconstruct how the Asian monsoon evolved over the past 66 million years.

The findings show that the monsoon began as a weak seasonal circulation before gradually intensifying as Earth’s topography changed. As the Tibetan Plateau rose to heights exceeding about 3.5 kilometres between roughly 27 and 38 million years ago, it altered atmospheric circulation by heating the air above it, strengthening temperature contrasts in the upper atmosphere and pushing the monsoon rainbelt northward. 

This process significantly increased rainfall across South and Southeast Asia, expanding a system that initially delivered strong summer rains mainly to East Asia. While the collision between the Indian and Eurasian plates influenced regional rainfall patterns, the study indicates that the vast elevated landmass of the Tibetan Plateau was the dominant factor behind the monsoon’s strength and geographic spread. 

The research also found that after the late Miocene period, declining atmospheric carbon dioxide levels began to modulate monsoon intensity, though tectonic uplift remained the primary influence. By highlighting how geological forces shaped climate over millions of years, the study improves understanding of past climate records and strengthens projections of future monsoon behaviour in a region that supports nearly half of the world’s population.