The 2023-24 El Niño Boosts Global Mean Surface Temperatures to a New Record High 1.5°C Above Preindustrial Levels

Global mean surface temperature (GMST) reached a new record in 2024, exceeding pre-industrial levels by approximately 1.5 °C for the first time. The long-term rise in GMST is driven by Earth’s radiative imbalance at the top of the atmosphere, caused by human-induced increases in heat-trapping greenhouse gases. Superimposed on this long-term warming trend are natural variations like those associated with El Niño and La Niña. Following an unusual triple-dip La Niña from 2020 to 2023, a strong El Niño developed in boreal spring 2023 and persisted through mid-2024. From the final year of the La Niña (July 2022–June 2023) to the subsequent year encompassing the 2023–24 El Niño (July 2023–June 2024), GMST rose by an unprecedented 0.36 °C to 1.5 °C above the 1850-1900 average. This presentation demonstrates that the primary driver of this abrupt increase in GMST was the release of heat previously stored in the ocean during the prolonged La Niña, which was rapidly transferred to the atmosphere during the 2023–24 El Niño event.