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 not yet known, but it is, I think, more likely than not," the director of the EU's Copernicus Climate Change Service 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.