11:15 〜 11:30
[ACG38-09] The triple-dip La Niña was key to Earth’s extreme heat uptake in 2022-2023
キーワード：地球エネルギー非平衡、放射収支、内部変動、エルニーニョ・南方振動
Recent observations reveal a surge in Earth's energy uptake in 2022/23, reaching 1.94 W/m2 (yearly average from October 2022 to September 2023). This increase played a pivotal role in the record-high global surface temperatures and widespread climate extremes observed by early 2024. However, its attribution remains challenging due to limited understanding of internal climate variability’s influence on Earth’s energy imbalance. Here, using multi-model climate simulations, we show that the transition from a three-year La Niña to a strong 2023/24 El Niño was a key driver of the extreme 2022/23 energy uptake, superimposed on the ongoing positive trend of Earth’s energy imbalance (EEI) due to anthropogenic forcing. We find that simulation samples with extreme global energy uptake systematically accompany preceding multi-year La Niña and subsequent El Niño, consistent with observations. These samples also replicate the dominant contribution of the shortwave radiation anomaly to the net energy imbalance and spatial distributions of radiation and atmospheric circulation anomalies organized by El Niño-Southern Oscillation (ENSO). Further analyses using targeted sampling of ENSO transitions reveal that the La Niña-to-El Niño sequence contributed 0.58 (±0.04) W/m² to the enhanced energy uptake, with the multi-year persistence of La Niña alone accounting for an additional 0.23 W/m².When combined with the external forcing component (~1.1 W/m²) estimated from large ensemble simulations, the enhancement of EEI associated with internal variability can closely account for the extreme EEI observed in 2022/23.Our finding illustrates the striking influence of internal climate variability, in addition to anthropogenic forcing, on Earth's energy budget and underscores their significance in past and future global climate extremes.