The study predicts fewer, but more destructive cyclones due to global warming

Cyclone Amphan which ravaged South Bengal and Bangladesh in May 2020 was the lone super cyclone to sweep the Bay of Bengal since the catastrophic storm of 1999 that claimed more than 10,000 lives. Even though super cyclones have been rare in the north Indian ocean, the region is known to be a hotbed of tropical storms with over 14 cyclones being reported from the water body in the last two years.

A new study commissioned by South Korea’s Institute of Basic Science at Pusan National University has predicted that the tropical storms hitting India in the future might be more devastating. The study which spanned over 13 months projects that an increased number of category 3 or higher tropical storms are likely to cross coasts of Indian and Pacific Oceans in the future due to climate change. According to the Indian Meteorological Department’s classification, a category 3 or higher storm on the Saffir-Simpson scale is usually equivalent to an ‘extremely severe’ or ‘super’ cyclone. 

However, there is also a silver lining in this gloomy picture. Based on model simulations on South Korean supercomputer Aleph, the study projects that the number of tropical storms in the region is likely to decline as the earth’s temperature rises. 

The study talks about how a reduction in rising motion in the tropical atmosphere will follow an increase in the quantum of carbon dioxide, which will hamper the development of cyclones. However, the cyclones that do develop will come in contact with high levels of energy and humidity and will quickly develop into powerful storms.

Dr. Sun-Seon Lee, who conducted the simulations on the supercomputer Aleph, said that the phenomenon explained the projected suppression of tropical cyclones. He also said that the pattern of simulations for future cyclonic changes was similar to trends observed recently, thereby cementing claims that global warming was behind extreme weather conditions across the world.

Increased risk of coastal flooding

The study also claims that an increase in sea surface temperatures by 1.8 degrees Celsius to 3.7 degrees Celsius was correlated to a surge in rainfall induced by cyclones. It was found that cyclone-induced rain had increased by up to 9.5%. The surge in rainfall might lead to coast areas being flooded as cyclones usually lead to massive rain during and after their landfall. However, the researchers have come across an earlier unknown concept which is referred to as the ‘saturation limit’ of global warming. The limit was pegged at 5 degrees Celsius. Beyond this limit and ignoring a potential ecological disaster, high-intensity storms are likely to reduce and subside. That being said, the simulations projected that coastal flooding would continue to ravage areas so long as global warming continues.

The lead author of the study Dr. Jung-Eun Chu said that rain linked to each event would still increase and thereby increase the risk of flooding to coastal areas. He claimed that the study offered important policy-relevant information for nations that are affected by tropical cyclones.

Hurdles in assessing the damage caused by global warming

Talking about natural calamities, cyclones are one the most damaging and catastrophic ones which often lead to hundreds of lives being lost and billions of dollars being spent in rescue and relief efforts every year. Take the Cyclone Amphan for example, which killed over 120 people and unleashed damage worth US$13 billion. Seen as a factor that exacerbates the threat, ocean warming has contributed to the increase in the pace with which a cyclone intensifies. The trend has also been observed over the last few years. As research shows that climate change will continue to hamper life on earth over the next few years, it becomes important that people understand the effect of natural calamities like cyclones.

One of the biggest challenges in assessing the impact of a phenomenon like global warming on cyclones is that the limited computing ability over the past several years. The level of complexity that is encountered in getting atmospheric details and then simulating an interaction between oceanic and atmospheric processes in uncertain conditions is beyond the capability of even the fastest supercomputers in the world. However, given the advancements in computing technologies and model simulations with each passing year, experts are fine-tuning projections so that they become more dependable.

Detail-oriented simulations

The South Korean researchers used high-resolution simulations from supercomputer Aleph for the study to overcome the limitations of computing. A statement issued by the institute said that the results of the study showed that while climate change will intensify cyclones, it will also arrest the development of weaker events. The research has been described as one of the most detailed and computing-intensive studies to have been done so far.

During the study, the supercomputer Aleph used horizontal scales of 25 kilometers and 10 kilometers for simulating small-scale atmospheric and oceanic processes respectively. It used the data for understanding how global warming affected the formation of a cyclone in the Indian Ocean and the Pacific Ocean.