Researchers said the El Niño, now strengthening, is on course to be the largest in at least 150 years, according to the multidisciplinary science journal Nature.
If forecasts hold, the heat it releases from the ocean, combined with human-caused climate change, will also trigger extreme weather across much of the world.
Climate models project that this El Niño's peak will surpass the previous record by "truly a mind-blowing margin," according to Zeke Hausfather, a climate scientist at Berkeley Earth, a U.S.-based non-profit that hosted the briefing.
He said it is "not outside the realm of possibility" that the event, combined with climate change, could push global average temperatures in 2027 as high as 1.7°C above pre-industrial levels, bringing the planet to the edge of breaching the 1.5°C threshold that governments pledged to avoid under the Paris Agreement.
"For context, the gap between the strongest and the fifth strongest El Niño of the past 150 years is only about 0.5C. The models are forecasting something outside the envelope of anything we have ever observed."
