Climate change will make severe cyclones the new normal

Tropical storms are a fact of life, but while South Asia has not seen a marked increase in the number of storms each year, the devastation left in their wake has become even more severe.

According to the United States' National Oceanic and Atmospheric Administration (NOAA), the average number of named storms (those reaching tropical storm strength) globally per year has remained relatively stable over the past few decades, hovering at around 80-90 on average.

However, the number of high-intensity storms -those classified as Category 4 or 5- has increased. Data from the Intergovernmental Panel on Climate Change (IPCC) supports this trend, indicating that the proportion of Category 4 and 5 storms has increased over recent years.

A major force behind this trend is the rise in sea surface temperatures. Warmer waters provide more energy for storms, enabling them to grow in strength and sustain higher wind speeds. When added to rising sea levels these storms are able to flood water inland with greater ease as the average height storm surges continue to rise.

Bangladesh and West Bengal have historically been highly vulnerable to cyclones due to its geographic and socio-economic conditions. The Bay of Bengal has been a hotspot for some of the deadliest cyclones in history, and recent trends suggest that the intensity of these storms will only continue to increase.

Data from the Bangladesh Meteorological Department (BMD) and other regional meteorological departments show a noticeable rise in the frequency of severe cyclonic storms over the past two decades. Between 2001 and 2020, the Bay of Bengal witnessed an average of 15 cyclones per year, with a significant number of those developing into severe cyclones.

The Super Cyclonic Storm Amphan in May 2020 is an example of this trend. It was the first super cyclonic storm in the Bay of Bengal since 1999, causing extensive damage in Bangladesh and India, with wind speeds exceeding 240 km/h. Similarly, Cyclone Fani in 2019 and Cyclone Phailin in 2013 were among the strongest storms to hit the region in recent memory, both causing widespread devastation.

Climate models predict that the trend of increasing storm severity is going to continue. The IPCC's Sixth Assessment Report highlights that with continued global warming, the frequency of the most intense storms (Category 4 and 5) will likely rise further.