El Niño and Record Warm SSTs Boost Global Mean Surface Temperatures

According to the World Meteorological Organization, 2024 is the warmest year on record and the first year of the modern era that global mean surface temperatures have likely exceeded pre-industrial levels by 1.5°C.  Temperatures in 2024 surpassed the record set in 2023, which is now the second warmest year of the modern era. The record warmth in 2023-2024 was accompanied by extraordinary weather and climate extremes around the globe including historic droughts and floods, widespread wild fires, and intense and prolonged marine heatwaves. Human-caused increases in heat trapping greenhouse gas concentrations are the fundamental underlying cause for these record high global mean surface temperatures, with atmospheric carbon dioxide levels reaching new highs in 2023 and 2024.  Coincidentally, after nearly a decade of near-neutral or unusually cold conditions in the tropical Pacific, an El Niño that ranked among the strongest of the past 75 years emerged in the boreal spring of 2023 and peaked at the end of the year before decaying in the spring of 2024. This presentation will show that heat loss from the ocean to the atmosphere during the El Niño was primarily responsible for boosting global mean surface temperatures into record territory in 2023 and 2024, though elevated sea surface temperatures in other parts of the world ocean contributed to these global temperature extremes.