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Planet> Climate change Updated: 25 Aug 2023

El Niño is back in 2023: What does this mean for the climate?

World Meteorological Organization (WMO) experts have just warned that El Niño, a natural phenomenon that arises in the Pacific Ocean and shapes weather around the world, has started up again. So their forecasts, which a few months ago indicated that there was a 55% chance that El Niño would re-emerge in the second half of 2023, have proven to be accurate. But this is bad news. Because El Niño poses the danger of a new global temperature change.

Even before science could accurately explain the phenomena that explain the Earth's climate, Peruvian fishermen observed that every few years a warm current dominated the waters of the Pacific. This recurring event was dubbed El Niño, 'the Child,' because its effects were felt most strongly in December, falling on Christmas Day.

Today we know that El Niño is a climate factor that arises in the Pacific Ocean and shapes the weather all over the world. According to the World Meteorological Organization, there was a 55% probability that the El Niño phenomenon would occur in the second half of 2023. This could lead to a global increase in temperatures and change wind and rainfall patterns around the world.

What are El Niño and La Niña?

El Niño and La Niña are different phases of a climate pattern that repeatedly occurs in the tropical zone of the Pacific Ocean and is known as ENSO (El Niño-Southern Oscillation). El Niño is a warming phenomenon, while La Niña is a cooling phenomenon. The two factors follow one after the other, although there are often neutral conditions between them.

During El Niño events, the Pacific surface warms, surface winds weaken and rainfall increases in the southern and eastern part of the ocean. All this causes changes in air pressure at sea level, in temperature, in rainfall and in winds, not only in the tropics, but also in many other regions of the world.

La Niña events, however, have the effect of cooling the surface of the Pacific Ocean. The consequences, like those of El Niño, can be felt all over the planet. Since September 2020, the world has been under the effects of La Niña: it has been felt, for example, in the Horn of Africa and some regions of South America in the form of strong droughts, contrasting with heavy rainfall in Southeast Asia and Australasia.

After three consecutive years dominated by La Niña, the El Niño warming phenomenon could begin to gather momentum in the Pacific in the second half of 2023. According to the WMO, there is more than a 50% chance of this happening, although, as is often the case with meteorology, this is still fraught with uncertainty.

How will El Niño affect the weather?

El Niño and La Niña are natural phenomena. Unlike climate change, they are not anthropogenic in origin. However, the consequences of natural and man-made factors can combine. This was the case in 2016, the warmest year since records began, due in large part to a combination of El Niño and the effects of climate change.

Since El Niño is a warming phenomenon, global temperatures are expected to rise over the next few years. "There is a 93% probability that at least one year between 2023 and 2026 will be the warmest on record, and a 50% probability that global temperature will temporarily reach a rise of 1.5°C above the pre-industrial era average," the WMO has stated.

This leaves the planet in a vulnerable predicament, as the past eight years have already been the warmest period ever recorded (despite the influence of the La Niña cooling phenomenon for three years) due to the effects of anthropogenic climate change.

It is crucial to understand that a rise in global average temperatures does not imply that it will be warmer all year round in all regions of the world. In some areas, in fact, climatic phenomena caused by El Niño may lead to a drop in temperatures. This is the case in Northern Europe, where winters can be drier and colder due to the behavior of the jet stream.

The jet stream, a current of powerful winds that carries rain across the Atlantic, may also make conditions wetter in Southern Europe. On the other side of the globe, in Australia, El Niño may mean less rainfall and higher temperatures, increasing the risk of droughts and forest fires.

In Latin America, close to the Pacific Ocean where the warming phenomenon originates, weather patterns are also likely to undergo serious changes. Tentative predictions point to a drier than usual season in the Amazon, for example.

Climate phenomena often act like strategically placed dominoes: when one topples over, there is a cascading effect on all the others. Today, it is impossible to predict exactly what the consequences of the return of El Niño will be, or when it will occur. We can, however, anticipate a period of warming that will combine with the effects of climate change we already experience in our day-to-day lives.