Human activities, and their impact on climate and the environment, may have influenced Cyclone Amphan in several ways, multiple experts have said.
Cyclone Amphan is gathering momentum to become the strongest storm on record in the Bay of Bengal with sustained wind speeds of 270 km per hour, making it stronger than the 1999 super cyclone and the joint strongest on record in the North Indian Ocean.
Climate change is increasing the damage that cyclones cause in many ways, including increasing sea surface temperatures that raise the maximum potential energy that a storm can reach; increasing the rainfall that drops during the storm; rising sea levels, which increases the distance inland that storm surges reach; and causing storms to gain strength more quickly.
Scientists are discovering a complex relationship between air pollution and cyclones, and it is possible that reductions in air pollution in the region, due to the COVID-19 restrictions, may have influenced Cyclone Amphan. Although they agree this requires further investigation.
One factor is that aerosols reduce the amount of sunlight reaching the earth’s surface, cooling it slightly. Reductions in air pollution may have slightly increased sea surface temperatures in the Bay of Bengal, adding to the effect of climate change.
In addition, aerosols can make clouds produce rain more easily, which limits the formation of cyclones. These factors suggest that reductions in air pollution would tend to increase cyclone strength.
another factor that influences cyclone strength, wind shear, has the opposite relationship with air pollution.
Higher air pollution tends to reduce wind shear, which generally allows stronger cyclones to form. So reduced air pollution could, in this respect, limit cyclone strength.
So while there may be a relationship between the reduction in air pollution, due to the Covid-19 restrictions, and Cyclone Amphan, it is too soon to say exactly what influence cleaner air has had on the storm.
Roxy Mathew Koll, a scientist with the Indian Institute of Tropical Meteorology and lead author of the United Nations’ Intergovernmental Panel on Climate Change (IPCC) oceans and cryosphere, said, “Our research shows that high ocean temperatures are conducive for rapid intensification of cyclones in the North Indian Ocean. “In the current case, the Bay of Bengal has been particularly warm, which may have had some role in the rapid intensification from a depression to a cyclone and then to a super cyclone in a very short time.”