Arabian Sea tropical cyclones have become stronger over the past 30 years owing to a reduction in vertical wind shear (VWS) brought about by radiative forcing from pollution aerosols1. Wang et al.2 argue that the decline in VWS results from a systematic shift in storm genesis date, which may be part of a natural cycle or another consequence of regional pollution. However, their conclusions2, although interesting, are not supported by our analysis and are probably sensitive to biases in the observational record.