Climate change that doesn’t make cyclones like the one hitting Bangladesh more frequent, but it does make them more intense and destructive, according to climatologists and meteorologists.
These extremely powerful natural phenomena have different names depending on the area they hit, but cyclones, hurricanes and typhoons are all violent tropical storms that can produce 10 times more energy than the Hiroshima atomic bomb. They are divided into different categories based on the maximum sustained wind power and the extent of the damage they can potentially cause.
Cyclones, storms and hurricanes
“A cyclone is a low-pressure system that forms in the tropics in an area warm enough to develop,” Emmanuel Clope, from the French meteorological service Météo France, told AFP. “It is characterized by rain/thunderstorm clouds that begin to turn and generate heavy rain and winds, as well as a wind-driven storm surge,” he added. These massive weather features, hundreds of miles in diameter, are made more dangerous by their ability to travel great distances. Tropical cyclones are classified according to the intensity of their winds, ranging from tropical depression (below 63 km/h), through tropical storm (63-117 km/h) to hurricane major (greater than 115 km/h).
They are called cyclones in the Indian Ocean and the South Pacific, storms in the North Atlantic and the northeast Pacific, and hurricanes in the northwest Pacific. The meteorological services that monitor them use different scales to categorize them, depending on the ocean basin in which they occur. The best-known scale for measuring their intensity and destructive potential is the five-point Saffir-Simpson wind scale.
more powerful cyclones
“The total number of tropical cyclones per year has not changed globally, but climate change has increased the frequency of more intense cyclones and catastrophic storms», according to the World Meteorological Report (WWA), a group of climatologists and climate impact experts whose objective is to demonstrate reliable links between global warming and certain meteorological phenomena. The strongest cyclones – categories three to five on the Saffir-Simpson scale that cause the most damage – have become more frequent, WWA said. Climate change caused by human activity affects tropical cyclones in three main ways: by warming the air and oceans and by causing sea levels to rise. “Tropical cyclones are the most extreme precipitation events on the planet,” says WWA in its report on extreme weather and climate change.
Since the atmosphere is warmer, it can hold more water, so when it rains, it rains. “An increase in air temperature of three degrees Celsius can potentially lead to a 20% increase in the amount of rain produced by a hurricane event,” Klopp said.
These heavy torrential rains lead to sometimes deadly floods and landslides, as was the case with Cyclone Freddy, which killed hundreds of people in Malawi and Mozambique earlier this year. Climate change is also warming the oceans. This hot water feeds the cyclones and gives them their strength.
“Climate change is therefore creating the conditions under which more powerful storms can form, rapidly intensify and persist to make landfall, while carrying more water,” WWA said.
The strong winds generated by cyclones create storm surges that can cause coastal flooding. These storm surges are now higher than in previous decades due to sea level rise caused by climate change. Scientists also expect to see cyclones in places they haven’t before, as global warming expands areas where tropical seawater conditions occur. “It’s as if the tropics are expanding,” Klopp said.
“Areas that are not really affected now could be much more so in the future.” WWA agreed: “As ocean waters warm, it is reasonable to assume that tropical storms will move away from the equator. “The northward shift of cyclones in the western North Pacific, affecting East and Southeast Asia, is a direct consequence of climate change,” he said. As a result, they could hit relatively unprepared spots that they had no reason to expect in the past.