Explain the El Niño weather phenomenon to us

According to a study by the World Meteorological Organization, published Wednesday, El Niño is responsible for temperatures above seasonal averages. A phenomenon which should continue until May over most of the planet.

El Niño is this natural meteorological phenomenon, of variable intensity and now predictable, which returns every three to seven years on average and which, for a few months, modifies the atmospheric circulation in the Pacific at the level of the equator, notably leading to a rising water temperatures in this region and a range of weather disturbances. It therefore first has a local impact, particularly this year along the coasts and in the countries bordering the eastern Pacific area, it is particularly singled out for having aggravated the fires which ravaged Chile in February 2024.

An effect on the planet’s atmospheric circulation

Numerous studies have been carried out over the past 40 years on this phenomenon and today, the scientific consensus admits that El Niño in fact modifies atmospheric circulation on a planetary scale, firstly over all equatorial zones, but also at more mid-latitudes, hence the fact that we can see its effects in California for example.

This time, El Niño appeared last June, peaked in December and January, and gradually declined in intensity until its expected disappearance in May, hence the World Meteorological Organization’s conclusion that it was likely exceeding seasonal averages for a few more months.

Greenhouse gases: main cause of warming

These gas emissions such as CO2 or methane are first of all responsible for the rise in average temperatures, this is the main cause and El Niño only occasionally accentuates the phenomenon, adding 0.1 or 0.2 degrees. It is therefore above all the increase in carbon emissions or equivalent and their accumulation in the atmosphere which leads to the lasting rise in temperatures, with, in the end, a year 2023 in second position on the podium in terms of ocean temperatures and in pole position if we look at average air temperatures.

One last piece of data, on a French scale, this time, monthly temperatures have been above the reference averages since February 2022, two years non-stop, if we put aside April 2023 where we were right on average. This goes well beyond our El Nino cyclical phenomenon, which could however be modified by this climate change. This is one of the questions that scientists are working on.