Enhanced Hemispheric Thermal Contrast Intensified the Indian Monsoon
During the Last Interglacial
Observational data from the past century show a weakening trend in
summer monsoon over the Indian subcontinent. This is possibly attributed
to the reduced land–sea contrast resulting from the Indian Ocean
warming under the rapid increase of greenhouse gases in the atmosphere.
In contrast, speleothem records indicate that the Indian summer monsoon
was stronger during the last interglacial (LIG) warm period than it is
today. Using climate model simulations, we show that orbital forcing
effect during the LIG, as well as related ocean feedbacks, led to
warming in the Eurasian continent and cooling in the Indian Ocean basin.
This amplified the land–sea contrast in the region and intensified the
Indian summer monsoon. Although the LIG is often portrayed as a
potential analogue of future climate, our study shows that the Indian
monsoon responded differently to the LIG warming period than it does to
current climate warming.