Increase in the Asian Southwest Monsoon During the Past Four Centuries

TLDR

Climate reconstructions show unprecedented warming in the past century, yet trends in monsoon aspects remain poorly understood. The study reconstructed past monsoon winds from Globigerina bulloides abundance in Arabian Sea cores, revealing a four‑century increase linked to Northern Hemisphere warming, and suggests that volcanic aerosols, solar output, and greenhouse gases may directly drive this trend. The analysis indicates a persistent centennial link between Eurasian snow cover and southwest monsoon strength, and predicts that the monsoon will intensify in the coming century as greenhouse gases rise and northern latitudes warm.

Abstract

Climate reconstructions reveal unprecedented warming in the past century; however, little is known about trends in aspects such as the monsoon. We reconstructed the monsoon winds for the past 1000 years using fossil Globigerina bulloides abundance in box cores from the Arabian Sea and found that monsoon wind strength increased during the past four centuries as the Northern Hemisphere warmed. We infer that the observed link between Eurasian snow cover and the southwest monsoon persists on a centennial scale. Alternatively, the forcing implicated in the warming trend (volcanic aerosols, solar output, and greenhouse gases) may directly affect the monsoon. Either interpretation is consistent with the hypothesis that the southwest monsoon strength will increase during the coming century as greenhouse gas concentrations continue to rise and northern latitudes continue to warm.