PARIS: Deadly extreme weather on at least five continents is driven in large part by a record-breaking El Nino, but climate change is a likely booster too, experts said on Monday.
The 2015-16 El Nino phase, they added, was the strongest ever measured.
The El Nino effect, which emerges every four to seven years on average and runs from October through January, is triggered by a shift in trade winds across the Pacific around the equator. Warmer surface water that normally accumulates in the eastern Pacific moves to the west, leading to heavier rainfall along the west coast of the Americas and drier-than-usual conditions in Australasia and southeast Asia.
“It is probably the most powerful in the last 100 years,” Jerome Lecou, a climate expert at the French weather service Meteo France, said, noting that accurate measurements had only existed since the mid-20th century.
Flooding and mudslides unleashed by torrential rains have hit Paraguay, Argentina and Uruguay in recent days.
In central and southwest United States — where temperatures in Texas were forecast to drop from 28 degrees Celsius on Saturday to zero on Monday — clashing weather fronts have given rise to snow-packed blizzards, freezing rain and a spate of tornadoes.
Across the Pacific, meanwhile, wildfires in Australia have been fanned by high temperatures and super-dry conditions.
Across south and southeast Asia, monsoon rains essential for life-sustaining crops have been limited, while drought in east Africa means millions will require food aid, especially in Ethiopia, according to Oxfam.
“The role of El Nino on much of what we are seeing around the planet is obvious,” Herve Le Treut, a climate scientist and director of the Pierre-Simon Laplace Institute, which is a federation of French research centres, said.
This year’s El Nino was the most powerful ever measured, surpassing the one in 1997-98, both in terms of ocean surface temperature — up by more than 3C — and the surface area affected, Mr Lecou said.
As was true in 1998, this year’s super El Nino will have contributed to making 2015 the warmest on record, worldwide.
But the reverse may also be true, with climate change boosting the power of cyclical El Nino events.
“If you add the background global warming to natural weather phenomena, there’s a tendency to break records left and right,” Mr Le Treut told AFP.
“This naturally occurring El Nino and human-induced climate change may interact and modify each other in ways which we have never before experienced, “Michel Jarraud, head of the World Meteorological Organisation in Geneva, noted last month.
But the multiplier effect of climate change on extreme weather events — while predicted by climate models — is very difficult to establish on a case-by-case basis, scientists caution.
The tornadoes, for example, that ripped across populated stretches of the Dallas-Fort Worth metropolis in Texas cannot be directly linked to global warming, even if generally warmer conditions may favour their occurrence.
Likewise the heavy rains and flooding that have devastated parts of northern England.
“Milder winters favour rainfall, such as what we are seeing in England,” said French researcher Jean Jouzel, former vice chair of the UN’s top panel of climate scientists.
But such extremes could still fall within the boundaries of natural cycles, independent of climate change, he added.
This year’s El Nino is credited with the largest number -- nine, in total -- of major Pacific hurricanes in a single season, along with the single most powerful hurricane ever recorded.
Patricia, packing 320-kilometre per hour winds, was downgraded to a tropical storm by the time it struck Mexico in October.
Published in Dawn, December 29th, 2015