A US government forecaster on Thursday confirmed that El Nino conditions are now being seen, with farmers from Australia to India bracing for the possible hit to crops from the dry, hot conditions it could bring.
El Nino, a warming of water surface temperatures in the eastern and central Pacific Ocean, could gradually strengthen into the Northern Hemisphere winter 2023-24, the Climate Prediction Center (CPC) of the National Oceanic and Atmospheric Administration (NOAA) said in its monthly advisory.
Early signs of El Nino weather were already threatening food producers across Asia, while American growers are counting on heavier summer rains from the weather phenomenon to alleviate the impact of severe drought.
It could lead to winter crop production falling 34% from record highs in Australia, and also affecting palm oil and rice production in Indonesia, Malaysia — which supply 80% of the world’s palm oil — and Thailand.
In India, which largely depends on the monsoon rains for its summer crop, impacts from El Nino could be offset by the Indian Ocean Dipole, or the Indian Nino, yet below normal rainfall was expected over northwestern parts of the country.
At its peak, the chance of a strong El Niño is nearly the same as it was last month, at 56% chance during November-January, and an 84% chance of exceeding moderate strength, the NOAA forecast said.
While it was too early to draw parallels with the 2016 El Niño event, “it was very similar as far as the strength and the water temperatures that have started to rise, particularly so fast in the last couple months”, said Chris Hyde, a meteorologist at Maxar.
This year’s El Nino could lead to global economic losses of $3 trillion, according to a study published last month in the journal Science, shrinking GDP as extreme weather decimates agricultural production, manufacturing, and helps spread disease.
Governments in vulnerable countries are taking note. Peru has set aside $1.06 billion to deal with El Nino’s impacts and climate change, while the Philippines — at risk from cyclones — has formed a special government team to handle the predicted fallout.
Here is how El Nino will unfold and some of the weather we might expect:
What causes El Nino?
El Nino is a natural climate pattern borne out of unusually warm waters in the eastern Pacific.
It forms when the trade winds blowing east-to-west along the equatorial Pacific slow down or reverse as air pressure changes, although scientists are not entirely sure what kicks off the cycle.
Because the trade winds affect the sun-warmed surface waters, a weakening causes these warm western Pacific waters to slosh back into the colder central and eastern Pacific basins.
During the 2015-16 El Nino — the strongest such event on record — anchovy stocks off the coast of Peru crashed amid this warm water incursion. And nearly a third of the corals on Australia’s Great Barrier Reef died. In too-warm waters corals will expel living algae, causing them to calcify and turn white.
This buildup of warm water in the eastern Pacific also transfers heat high into the atmosphere through convection, generating thunderstorms.
“When El Nino moves that warm water, it moves where thunderstorms happen,” said NOAA meteorologist Tom DiLiberto. “That’s the first atmospheric domino to fall.”
How does El Nino affect the world’s weather?
This shift in storm activity affects the current of fast-flowing air that moves weather around the world — called the subtropical jet stream — pushing its path southward and straightening it out into a flatter stream that delivers similar weather along the same latitudes.
“If you’re changing where the storm highway goes … you’re changing what kind of weather we would expect to see,” DiLiberto said.
During an El Nino, the southern United States experiences cooler and wetter weather, while parts of the US West and Canada are warmer and drier.
Hurricane activity falters as the storms fail to form in the Atlantic due to changes in the wind, sparing the United States. But tropical cyclones in the Pacific get a boost, with storms often spinning toward vulnerable islands.
Some parts of Central and South America experience heavy rainfall, although the Amazon rainforest tends to suffer from drier conditions.
And Australia endures extreme heat, drought and bushfires. El Nino could offer a reprieve to the Horn of Africa, which recently suffered five consecutive failed rainy seasons. El Nino brings more rain to the Horn, unlike the triple-dip La Nina which desiccated the region.
Historically, both El Nino and La Nina have occurred about every two to seven years on average, with El Nino lasting 9 to 12 months. La Nina, which takes hold when waters are cooler in the Eastern Pacific, can last one to three years.
Is climate change affecting El Nino?
How climate change might be affecting El Nino is “a very big research question,” said DiLiberto. While climate change is doubling down on the impacts from El Nino — layering heat on top of heat, or excess rainfall on top of excess rainfall — it’s less clear if climate change is influencing the phenomenon itself.
Scientists are not sure whether climate change will shift the balance between El Ninos and La Nina, making one pattern more or less frequent. If ocean temperatures are rising across the board, it is unlikely the cycle would change, scientists said, as the basic mechanics behind the phenomenon stay the same.
However, if some parts of the ocean are warming faster than others, that could influence how El Nino plays out by amplifying temperature differences.