Global warming drives an increase in pre-monsoon tropical cyclone activity over the North Indian Ocean.

Shan, Kaiyue; Song, Fengfei; Lin, Yanluan; Chu, Pao-Shin; Wu, Lixin; Yu, Xiping · Nat Commun · 2026

basic_science · Level V

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Abstract

Early-season tropical cyclones (TCs), particularly in the pre-monsoon period (April-June) of the North Indian Ocean (NIO) basin, often cause exceptionally severe damage to populated landmasses despite being less frequent. A critical uncertainty is how these TCs respond to anthropogenic climate change. Here, we find a significant increasing trend in pre-monsoon TC activity in the NIO basin, with accumulated cyclone energy exhibiting a striking rise of 3.01 × 10<sup>4</sup> knots<sup>2</sup> per decade (P  <  0.05) during 1981-2023, while the corresponding trend during the post-monsoon season (October-December) is weaker and insignificant. Climate models identify increased greenhouse gas as the primary driver, creating more favorable thermodynamic conditions for TC formation and maintenance in the NIO basin during the pre-monsoon season. These enhanced thermodynamic conditions are projected to intensify further, suggesting the increasing trend in pre-monsoon TC activity may continue to accelerate in the future.