This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The South Asian summer monsoon has long been known to shape the Mediterranean climate thousands of kilometers away as part of a phenomenon known as the "monsoon–desert" mechanism. Through this mechanism, intense monsoon convection during the summer releases large amounts of heat into the atmosphere, triggering large-scale circulation changes that promote sinking air over the Mediterranean.
This process suppresses clouds and rainfall and contributes to the Mediterranean region's hot, dry climate. Previous studies showed that heating associated with the South Asian monsoon helps drive this descending circulation. However, scientists have been unsure whether this long-distance atmospheric connection would persist under global warming.
To address this question, a research team led by Zhou Tianjun at the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences (CAS) combined real-world observations, dozens of climate model simulations and idealized numerical experiments to see how climate change under a future high-emissions scenario would affect this monsoon–Mediterranean link. The study is published in Nature Geoscience. The results showed a remarkably consistent signal.
In 97.5% of the CESM1 simulations, the South Asian monsoon had a weaker effect on atmospheric circulation over the Mediterranean. The relationship between monsoon heating and mid-tropospheric subsidence over the central and eastern Mediterranean declined from a correlation of about 0.4 to essentially zero by the second half of this century. To understand why the monsoon's remote influence on the Mediterranean is expected to weaken, the researchers examined the underlying atmospheric processes.
They identified one key change anticipated over South Asia. As the climate warms, deep monsoon convection shifts higher in the troposphere. In the CESM1 simulations, the characteristic level of monsoon convection shifts from about 452 hPa to 417 hPa, with a similar upward shift appearing across CMIP6 models.
As a result, the warm response produced by monsoon heating spreads farther west and reduces the east-west temperature contrast over the Mediterranean, which in turn suppresses subsidence through atmospheric dynamics. A second process occurs locally over the Mediterranean. The monsoon-related sinking motion weakens most strongly in the middle and upper troposphere.
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