Warming waters and rising sea levels are affecting Indian Ocean cyclones such as those that have wrought havoc in Mozambique in recent weeks, making them potentially more deadly.
But experts caution it is premature to say whether the unprecedented double-whammy of storms to hit the southern African nation is a consequence of climate change, and whether these cyclones will become more common.
Cyclone Idai, which swamped large parts of central Mozambique last month, killed over 600 people and displaced thousands. Cyclone Kenneth made landfall Thursday evening in the north of the country where no such storm has been recorded since satellite observations began in the 1970s.
“There is no record of two storms of such intensity striking Mozambique in the same season,” said Clare Nullis, a spokeswoman for the World Meteorological Organization.
“It is difficult to pronounce on one event like Idai, or even two like Idai and Kenneth. The statistical size of the sample is just too small,” she said. “But one thing is sure: The vulnerability of coastal areas will become worse with the sea-level rise induced by global warming.”
Inland areas, too, are at risk because storms are getting wetter. Kenneth, which has weakened to a tropical depression, is expected to bring heavy rainfall to already saturated soil and dams at the end of the rainy season.
“While attention is often given to wind speed, we know from experience that it is rainfall — and subsequent flooding and landslides — that can be even more dangerous from a humanitarian perspective,” said Antonio Carabante, an emergency relief delegate with the International Federation of Red Cross and Red Crescent Societies.
“This was certainly the case for Cyclone Idai,” Carabante said, adding that many affected areas are prone to flooding and landslides even with normal levels of rainfall. “And this is far from a normal situation.”
Such conditions can be particularly devastating for developing countries like Mozambique and neighboring Malawi and Zimbabwe, all hit by Cyclone Idai, where food stores can be quickly depleted in a disaster and the health care system struggles to cope with a sudden disease outbreak like cholera.
“Cyclone Kenneth may require a major new humanitarian operation at the same time that the ongoing Cyclone Idai response targeting 3 million people in three countries remains critically underfunded,” said the U.N.’s emergency relief coordinator, Mark Lowcock, who described the situation as a “climate-related disaster.”
Abubakr Salih Babiker, a meteorologist at the Nairobi-based Intergovernmental Authority on Development, said there are indications that tropical cyclones are becoming more common off East Africa as rising sea surface temperatures are a key ingredient for cyclones to form.
“There’s a pattern here,” he said, citing recent violent storms from Somalia in the Horn of Africa down to Mozambique. “What used to be rare is not rare anymore.”
And just as warmer seas are helping spark cyclones, hotter air is feeding the resulting rainfall, Salih Babiker said. “If the air is warmer, it has more ability to hold moisture.”
The World Meteorological Organization said this year’s cyclone season in the southwest Indian Ocean has been exceptionally intense, with 15 storms including nine intense cyclones. It is now tied with the record season of 1993-1994.
Nullis said the agency is sending an expert delegation to Mozambique to discuss with the government how to improve its resilience to extreme weather. Long and narrow with a 2,400-kilometer (1,500-mile) Indian Ocean coastline, the country is one of the world’s most vulnerable to global warming.