'Moderate to Strong' La Nina Expected This Year, Says U.N.
Global temperatures boosted by climate change will still be higher than usual despite the cooling effect of a "moderate to strong" La Nina weather phenomenon, the U.N. said Thursday.
The World Meteorological Organization (WMO) said La Nina "has developed and is expected to last into next year, affecting temperatures, precipitation and storm patterns in many parts of the world."
La Nina is considered the stormy sister of El Nino, which occurs every two to seven years when the prevailing trade winds that circulate surface water in the tropical Pacific start to weaken.
El Nino, which has a major influence on weather and climate patterns and associated hazards such as heavy rains, floods and drought, has a warming influence on global temperatures, whilst La Nina tends to have the opposite effect.
But global warming could worsen or distort the effects of such phenomena, WMO chief Petteri Taalas warned in a statement.
"All naturally occurring climate events now take place against a background of human-induced climate change which is exacerbating extreme weather and affecting the water cycle," he said.
"La Nina typically has a cooling effect on global temperatures, but this is more than offset by the heat trapped in our atmosphere by greenhouse gases," he pointed out.
"Therefore, 2020 remains on track to be one of the warmest years on record and 2016-2020 is expected to be the warmest five-year period on record," Taalas said.
"La Nina years now are warmer even than years with strong El Nino events of the past."
The last La Nina, which was brief and rather weak, began developing in November 2017 and ended in April 2018, according to WMO.
This year's La Nina "is expected to be moderate to strong", WMO said, adding that the world had not seen a strong La Nina for a decade.
WMO stressed though La Nina and El Nino were not the only factors driving global and regional climate patterns, and that "no two La Nina or El Nino events are the same".
"Their effects on regional climates can vary depending on the time of year and other factors," it said, urging decision makers to closely monitor seasonal forecasts and the latest data.
The U.N. agency pointed to fresh data indicating that this year's La Nina would among other things lead to below normal rainfall in the Horn of Africa region and Central Asia, while Southeast Asia, some Pacific islands and the northern part of South America would see more rain than usual.
Source: Agence France Presse
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