El Niño and Sea Surface Temperature Pattern Effects Lead to Historically High Global Mean Surface Temperatures in 2023

In 2023, the world experienced its highest ever global mean surface temperature (GMST). Our study underscores the pivotal significance of El Niño and sea surface temperature (SST) warming as the fundamental causes. Interannually, the increment of GMST in 2023 comprised two phases: first, gradual ocean warming associated with El Niño and the North Atlantic from January to August; second, a continued rise in land temperatures in the mid‐to‐high latitude regions from September onwards, influenced by SST patterns. Notably, the maturation of El Niño prolonged warming in North America through excitation of the Pacific‐North American teleconnection. During the most recent 15 years, GMST has entered an accelerated warming period, primarily driven by rapid SST warming trends in the tropical Indian Ocean, tropical Atlantic, subtropical North Pacific, and North Atlantic. These decadal warming patterns, combined with El Niño, may further increase GMST, with 2023 as a particularly striking example. Plain Language Summary In 2023, the world experienced its highest recorded surface temperatures. This study found that El Niño and sea surface temperature pattern effects played a significant role. The warming in 2023 had two phases: from January to August, the sea surface temperature gradually warmed, largely due to the development of El Niño and warming in the Atlantic; from September onward, land temperatures in the mid‐to‐high latitude regions sharply increased, mainly because of the warmer oceans. El Niño prolonged the warming in North America through the Pacific‐North American teleconnection. In the past decade or so, global warming trend has accelerated, mainly due to rapid warming trends in the tropical Indian Ocean, Atlantic, and subtropical North Pacific. These long‐term warming trends, combined with the 2023 El Niño event, led to the record‐breaking temperatures. Key Points Global mean surface temperatures set a new record high in 2023, significantly influenced by El Niño and sea surface warming There were two warming phases in 2023: ocean warming early, then land temperature warming later Recent rapid ocean warming has accelerated global temperature increases, with 2023 being a record year