Climate change likely driving early arrival of intense tropical cyclones: Study

NEW DELHI: Climate change may be driving the early arrival of the most intense tropical cyclone season, according to a study published in the journal Nature. Researchers from Tsinghua University in China and the University of Hawai'i at Manoa, US, found that intense tropical cyclones have tended to occur around three days earlier per decade since the 1980s.

The study shows that this seasonal shifting may be related to ocean warming, primarily driven by greenhouse gas emissions.

Intense tropical cyclones, defined as tropical cyclones with a lifetime maximum wind speed greater than 110 knots (203.7 km per hour), are one of the most devastating natural disasters, the researchers said.

Changes in characteristics of intense tropical cyclones -- including the number of cyclones, their intensities and lifespans -- are already well studied, but little is known about changes in their seasonal cycle, they said.

To investigate whether there have been changes in the seasonal cycle of tropical cyclones, researcher Xiping Yu and colleagues analysed satellite data from 1981 to 2017.

They found that the occurrence time of intense tropical cyclones shows a trend towards earlier onset, at a rate of 3.7 and 3.2 days per decade for the Northern and Southern Hemispheres, respectively.

However, the results showed that the seasonal advance is only notable for intense tropical cyclones, and not for less severe ones.

The earlier onset of intense tropical cyclones is shown to be associated with earlier increases of sea surface temperature and ocean heat content, which are driven mainly by greenhouse gas emissions, the researchers said.

The team examined data from South China and the Gulf of Mexico, two regions that are heavily affected by tropical cyclones, to investigate the potential effect of earlier intense tropical cyclones on extreme rainfall.

The results showed that the earlier onset of intense tropical cyclones contributes substantially to an earlier onset of extreme rainfall, accompanied by an increasing annual amount of persistent rainfall events.

Further research is needed to develop strategies to better protect people and regions at high risk of earlier intense tropical cyclones, the researchers added.