2020 likely to be one of warmest years on record despite La Niña.

Climate crisis exacerbates extreme weather during natural events, say experts.

La Niña climate event is under way, heralding a colder and stormier winter than usual across the northern hemisphere, but 2020 remains likely to be one of the warmest years on record.

The World Meteorological Organization (WMO) has declared La Niña event – a cooling of surface ocean water along the Pacific coast of the South American tropics – to help governments and humanitarian agencies plan for extreme weather events around the world.

La Niña (the little girl in Spanish) is the “cold” phase of El Niño southern oscillation, a series of oceanic and climatic events in the Pacific which exert a global influence on temperature, storms and rainfall.

Possible impacts in 2020 include drier than usual conditions in east Africa, adding to food security challenges in the region, wetter conditions across large parts of south-east Asia and Australia, and increasingly intense Atlantic hurricanes. In the Caribbean, the 2020 season has been one of the most active on record.

Petteri Taalas, the secretary general of the WMO, said: “El Niño and La Niña are major, naturally occurring drivers of the Earth’s climate system. But 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.”

While El Niño, the warm phase of the climatic phenomenon, can trigger drought in Australia and India, and increase cyclones in the tropical Pacific, La Niña can cause eastern Pacific sea temperatures to fall by up to 3-5C, which has a cooling effect on global temperatures.

According to Taalas, however, this is now more than offset by global heating, and 2020 “remains on track to be one of the warmest years on record”, with 2016-20 expected to be the warmest five-year period on record.

“La Niña years now are warmer even than years with strong El Niño events of the past,” said Taalas.

This year’s La Niña is expected to endure into the first quarter of next year and is rated by the WMO as “moderate to strong”. The last time there was a strong event was in 2010-11, which contributed to the 2010 Pakistan floods and the 2010-11 Queensland floods.

La Niña events are defined by sea surface temperatures falling by more than 0.5C for at least five successive three-month periods.

29 October 2020

The Guardian