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

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 × 104 knots2 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. Pre-monsoon tropical cyclones are particularly devastating in the North Indian Ocean. Global warming is increasing their activity, a trend likely to continue and raise risks for vulnerable coastal communities.