In the man-made climate crisis, the global average temperature is constantly rising, and with devastating consequences. The hottest year since industrialization began was 2016, and that comes as no surprise: in addition to the long-term trend, 2016 was marked by the El Niño weather phenomenon. It occurs naturally every few years and often pushes up the average global temperature.
Since this spring, signs of an El Niño have been rising again - and if it comes and gets strong, the global average temperature could top 2016 this year or next, experts warn. The World Weather Organization (WMO) wanted to explain on Tuesday whether El Niño is now in full swing or not.
What is an El Nino?
The first sign of the phenomenon is a strong warming of the upper water layers in the Pacific near the tropics, along the Central and South American coast. Actually, trade winds push the warm water to the west and cooler water flows in from deeper layers. In El Niño situations, however, the winds are weaker. The fast, ribbon-like jet stream is shifting south and the stratosphere more than 10 kilometers above the Earth is getting warmer, according to University of Maryland's Bob Leamon.
The counterpart to this is La Niña, with the opposite sign. La Niña depresses the global mean temperature. An unusually long three-year La Niña phase has just come to an end. Both phenomena happen at different intervals every few years.
Where does the name come from?
"El Niño" means the Christ Child. The name comes from fishermen in Peru who often noticed the temperature rise in the sea around Christmas time.
What are the consequences?
That depends on the world region. It will generally be drier and hotter in Southeast Asia, southern Africa and Australia. The risk of forest and bush fires is increasing there. In Australia, the hottest summer ever recorded was the turn of the year 2018/2019, which was marked by an El Niño. It is also becoming drier in Brazil and the northern part of South America, as well as in the Midwest of the USA, where there are often particularly good grain harvests in El Niño years. On the other hand, it is getting wetter in East Africa, which has just gone through a devastating drought, as well as on the west coast of North and South America and in Sri Lanka off the southern tip of India.
In the Gulf of Mexico, the risk of hurricanes decreases because there is less moisture in the air. Over the Atlantic, too, because stronger shear winds tear apart hurricanes, Leamon said. In the Pacific, on the other hand, there is a risk of more dangerous storms.
And Europe? "The El Niño fingerprint is concentrated in the tropical Pacific, with noticeable effects in the greater Pacific region and along the equator, but with only minor effects in Europe," says Helge Goessling of the Alfred Wegener Institute Helmholtz Center for Polar and Polar Sciences Marine Research (AWI) in Bremerhaven.
What is the trigger of an El Niño?
Science doesn't know yet. It is considered a natural phenomenon like the monsoon, but occurs at irregular intervals. What is known is that the strength of both El Niño and La Niña is influenced by other phenomena. If the trade winds normalize later in the year, as they did in 2014, an incipient El Niño may dissipate, NOAA climate scientist Michelle L'Heureux explains.
John Fasullo from the National Center for Atmospheric Research in the US state of Colorado believes that the most recent La Niña event lasted so long, for example, was due to the severe fires in Australia in 2019/20. Smoke aerosols in the atmosphere would have reflected sunlight, which cooled air layers over the Pacific and subsequently the sea surface.
Why does the average global temperature rise in El Niño years?
The climate scientist Richard Allan from the University of Reading has investigated this. On the one hand, satellite images and computer simulations in 2015/16 showed that more low-level clouds were dissipating over the Pacific and more sunlight was additionally warming the water. In addition, the atmosphere binds significantly more water than in other years. During strong El Niños, that could account for 3,000 cubic kilometers of water, as much as 120 million 50-meter swimming pools. "This helps further increase the heating power of El Niño, as water vapor is a powerful natural greenhouse gas," Allan said.
Is the goal of limiting warming to a maximum of 1.5 degrees if possible threatened by the approaching El Niño?
The target is in danger, but that's not because of El Niño. It's about different things. The 1.5 degree target from the Paris climate agreement - which experts say can hardly be reached - refers to an average value over several years.
Individual warmer years, which are now more likely due to El Niño, are not decisive for this. Even before the first signs of an El Niño, many scientists assumed that the 1.5 degree mark would soon be exceeded in a single year. After that, cooler years are likely to come again. According to the WMO, in 2022 the global average temperature was around 1.15 degrees above the level of 1850-1900. In 2016 it was around 1.3 degrees.
How strong will El Niño be in 2023?
Hard to say. With his model calculations, Leamon from the University of Maryland comes to the conclusion that the phenomenon is more likely to fizzle out this year and that a Super El Niño is not imminent until 2026.
What does this mean for the global economy and people?
According to calculations by US economists, the El Niños of 1982/83 and 1997/98 brought losses of up to 4.1 trillion dollars within five years - compared to a development without the weather phenomenon. The analysis company Economist Intelligence Unit sees a strong El Niño this year as a major risk for agricultural and fish production in South and Southeast Asia. That drives up food prices.
Higher temperatures could lead to energy bottlenecks with shutdowns there. This then affects industrial production. In Sri Lanka, heavier rain could affect tea production, while the humidity could boost dengue cases. The analysis institute Fitch Solutions warns of slumps in the grain harvest in southern Africa.