Return of El Niño phenomenon could push world over 1.5C mark next year, warns Irish expert

There is a 'reasonable chance' this year will be the warmest ever. File picture

There is a "reasonable chance" this year will be the warmest ever, but 2024 will "almost certainly be a new record" and may even cross the 1.5C mark, a leading climate change expert has said.

Maynooth University professor of geography climate change Peter Thorne said the expected return of the El Niño phenomenon would have a big bearing on whether the world would cross the 1.5C pre-industrial era warming threshold.

According to the landmark Paris Agreement of 2015 signed by 193 countries and the EU, a temperature rise limit of 1.5C is the number scientists say is needed to stave off the very worst climate-change fallout.

Prof Thorne stressed that while crossing the 1.5C threshold in a given year was highly symbolic of a globally warming world, it is the 1.5C mark averaging out over a longer period that would be of bigger significance.

Every effort to reduce greenhouse gas emissions will count so that 1.5C or higher does not become a long-term grim norm, he said. 

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The northern hemisphere has experienced the third winter of the La Niña water cooling phenomenon, in a highly unusual "triple dip" situation.

Opposite to the warming El Niño pattern, La Niña refers to the large-scale cooling of the ocean surface temperatures in the central and eastern equatorial Pacific Ocean, coupled with changes in the tropical atmospheric circulation, namely winds, pressure, and rainfall.

El Niño, in contrast, refers to warming of the ocean surface, or above-average sea surface temperatures, in the central and eastern tropical Pacific Ocean. 

It is now almost certainly on the way back, according to scientists, meaning it will gain strength over the remainder of the year and have a major bearing on 2024 temperatures.

Heatwaves and wildfires

A repeat of last summer's devastating heatwaves and wildfires across Europe is very possible, Prof Thorne said. Picture: Octavio Passos/Getty Images

A repeat of last summer's devastating heatwaves and wildfires across Europe is very possible, Prof Thorne said.

April was the joint fourth warmest April globally, but temperatures were above average over southwest Europe, with Spain and Portugal recording their highest ever April temperatures, according to the EU's Copernicus Climate Change Service.

Colder-than-average temperatures were experienced in a band stretching from the UK to southeast Europe.

Prof Thorne said: "We know that extremes become more frequent and more likely with increasing levels of warming. It doesn't follow that this summer will necessarily be similar to last, but the odds are inexorably rising. 

"It's not just on our doors in Spain and Portugal but even more in Asia where heat has been enveloping much of the southeast and centre of the continent for weeks on end, with several national records falling for many countries.

"It's not just El Niño, global sea surface temperatures have for weeks been anomalously high above normal records. El Niño is being increasingly forecast to occur and if it does, it will grow through the northern hemisphere summer and peak in our winter and perhaps early spring.

"Typically, there is a three-to-six month lag between El Niño temperatures and global temperatures so there is a reasonable chance now that 2023 might be a record warm year for global surface temperatures. 

"But if El Niño really kicks in, then 2024 will almost certainly be a new record and there is a chance, maybe not super-high, but that it could break through the 1.5C pre-industrial mark, albeit as one year and not on a long-term sustained basis," he said.

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