Increasing Frequency of Extremely Severe Cyclonic Storms over the Arabian Sea

In 2014 and 2015, post-monsoon extremely severe cyclonic storms (ESCS)—tropical storms with lifetime maximum winds greater than 46 m s⁻¹—were first observed over the Arabian Sea (ARB), causing widespread damage. However, it is unknown to what extent this abrupt increase in post-monsoon ESCSs can best be linked to anthropogenic warming, natural variability, or stochastic behaviour. Here, using a suite of high-resolution model experiments, we show that anthropogenic forcing has likely increased the probability of late-season ECSCs occurring in the ARB since the preindustrial era. However, the timing of observed late-season ESCSs in 2014 and 2015 was likely due to stochastic processes. It is further shown that natural variability played a minimal role in the observed increase of ESCSs. Thus, continued anthropogenic forcing will further amplify the risk of cyclones in the ARB, with corresponding socio-economic implications.