Air pollution may be strengthening the formation of tropical cyclones in the Arabian Sea, a US-based science agency has said, after Cyclone Vayu brushed past the west coast of India last week.Dr James Kossin, atmospheric research scientist at the National Oceanic and Atmospheric Administration (NOAA), said human-induced emissions like black carbon and sulphates increased six-fold since the 1930s. These, he explained, were responsible for weakening weather systems like wind shear (rapid changes in wind speed combined with direction or height of moving winds), which can otherwise prevent cyclones from forming during the pre-monsoon months. “There is evidence that air pollution over the Arabian Sea has caused a reduction of the wind shear. When this is combined with warming oceans, which help cyclones become stronger, it allows Arabian Sea cyclones to get stronger,” said Kossin, in a statement issued last week.The India Meteorological Department (IMD), however, reacted sceptically to the NOAA release, saying that, barring isolated statements, there is no proof of air pollution or climate change impacting cyclones. “We need not be concerned by such statements regarding air pollution aiding cyclone formation or weakening of monsoons,” said Dr KJ Ramesh, IMD director general. “The recent Intergovernmental Panel on Climate Change [IPCC] report, a body of the United Nations, has clearly indicated a positive anomaly for above normal rainfall for India, irrespective of a high or low emissions scenario,” added Ramesh. Despite IMD’s stance, local studies have also concluded that pollution is affecting the weather. Research by the Indian Institute of Technology-Bombay (IIT-B) in 2018, found that increasing anthropogenic aerosol emissions over a 40-year period (1971-2010) had influenced the suppression of South Asian monsoon rainfall.Air pollution researchers said emissions and their direct impact on the formation of cyclones need to be studied further. “A genre of scientific studies is coming up that are looking at the impact of black carbon and aerosols on monsoon, clouds, and cyclones. Several global studies have already confirmed the impact but we need to study this further, especially for India,” said Anumita Roy Choudhury, executive director, Centre for Science and Environment, Delhi.