Climate models suggest that after three years of the La Nina weather pattern in the Pacific Ocean, which generally lowers global temperatures slightly, the world will experience a return to El Nino, the warmer counterpart, later this year.
During El Nino, winds blowing west along the equator slow down, and warm water is pushed east, creating warmer surface ocean temperatures.
"El Nino is normally associated with record breaking temperatures at the global level. Whether this will happen in 2023 or 2024 is yet known, but it is, I think, more likely than not," said Carlo Buontempo, Director of the EU's Copernicus Climate Change Service.
Climate models suggest a return to El Nino conditions in the late boreal summer, and the possibility of a strong El Nino developing towards the end of the year, Buontempo said.
The world's hottest year on record so far was 2016, coinciding with a strong El Nino - although climate change has fuelled extreme temperatures even in years without the phenomenon.
The last eight years were the world's eight hottest on record - reflecting the longer-term warming trend driven by greenhouse gas emissions.
Friederike Otto, Senior Lecturer at Imperial College London's Grantham Institute, said El Nino-fuelled temperatures could worsen the climate change impacts countries are already experiencing - including severe heat waves, drought and wildfires.
"If El Niño does develop, there is a good chance 2023 will be even hotter than 2016 – considering the world has continued to warm as humans continue to burn fossil fuels," Otto said.
EU Copernicus scientists published a report on Thursday assessing the climate extremes the world experienced last year, its fifth-warmest year on record.
Europe experienced its hottest summer on record in 2022, while climate change-fuelled extreme rain caused disastrous flooding in Pakistan, and in February, Antarctic sea ice levels hit a record low.
The world's average global temperature is now 1.2C higher than in pre-industrial times, Copernicus said.
Despite most of the world's major emitters pledging to eventually slash their net emissions to zero, global CO2 emissions last year continued to rise.
