The culprit that caused unprecedented ferocity of storms Yagi and Helene

Faced with increasingly stronger storms, scientists have called for expanding the Saffir-Simpson scale to level 6 for storms with winds above 308km/h.

Scientists warn that climate change is increasing the destructive power of powerful storms to unprecedented levels , such as Hurricane Helene, which hit the southeastern United States, and Typhoon Yagi (Storm No. 3) that recently raged in Asia.

A recent study published in the US shows that global warming is the cause of tropical storms occurring with greater intensity and frequency.

Hurricane Helene caused severe flooding in Asheville, North Carolina (USA). This storm has so far killed at least 189 people, becoming the second deadliest storm in the US in the past 50 years - (Photo: AFP).

According to research, warming ocean surface temperatures cause an increase in water vapor in the atmosphere, making hurricanes stronger in intensity.

Michael Mann, a climatologist at the University of Pennsylvania, said that the current 1 degree Celsius increase in global temperatures has increased the destructiveness of hurricanes by about 40% on average. In a study published in the Proceedings of the National Academy of Sciences (PNAS), he called for an expansion of the Saffir-Simpson scale to a level 6 for storms with winds above 308 km/h.

Many scientists believe climate change increased the intensity of Hurricane Helene to Category 4 - the highest on the scale. Florida climatologist David Zierden said record levels of heat in the oceans helped intensify the storm and cause widespread damage.

Meanwhile, the phenomenon of "rapid intensification", meaning a storm's winds increase by 55km within 24 hours, is also becoming more common.

This increase could have serious impacts, especially if it occurs near the coast before a storm makes landfall, said Karthik Balaguru, a climate scientist at the US Department of Energy's Pacific Northwest National Laboratory .

Climate change is also reducing wind shear – changes in wind speed and direction with altitude – along the Atlantic coast of North America and the Pacific coast of Asia. 'Strong wind shear can prevent storms from developing and reduce their destructive power,' Balaguru explained.

In addition, the difference in temperature between the land surface and the water surface also causes high humidity along the coast, leading to pressure and wind circulation pushing moisture into the middle stratosphere, creating conditions for storms to develop.

In terms of frequency, some studies suggest that improved fine particulate pollution in the US and Europe may be increasing the frequency of hurricanes in the Atlantic, while pollution in China and India may be suppressing hurricanes in the western Pacific.