Tropical cyclones (TCs) are among the most destructive weather events, usually accompanied by intense winds, heavy rains, and massive storm surges. As global warming increasingly impacts our world, there is a growing curiosity within both the scientific community and the general public about how TC activity has evolved and may continue to change.

Historically, understanding of TCs and their relationship to climate change has been hindered by the brevity of observational data, typically covering less than 100 years. This limitation creates uncertainty regarding trends and variations in TC activity.  Understanding the response of TCs to past climate changes is crucial for predicting how they might react to ongoing global warming.

Recently, the research team led by Prof. YAN Hong, from the Institute of Earth Environment of the Chinese Academy of Sciences, developed the first daily-resolution proxy data for investigating prehistoric TC activity, using a 12-year growth rate record of a fossil Tridacna shell—an ancient bivalve found in the northern South China Sea dating back approximately 3,000 years.

The reconstruction revealed that unlike today’s TCs, which peak in the autumn months, those from 3,000 years ago were about 15% more frequent and primarily occurred during the summer. Combined with other paleoclimate records, the researchers propose that this seasonal shift was likely linked to a northward migration of the Intertropical Convergence Zone, creating favorable conditions for TC formation and development. This research offers a valuable perspective on the mechanisms and dynamics governing seasonal changes in TC patterns.

This work, published in npj Climate and Atmospheric Science, was supported by the National Natural Science Foundation of China, the National Key R&D Program of China, the fellowship from the China Postdoctoral Science Foundation and Innovation Capability Support Program of Shaanxi.