Causes and Predictions of 2022 Extremely Hot Summer in East Asia.

In the background of long‐term global warming, the northern hemisphere experienced an extremely hot summer in 2022 with the hottest on record for Europe and China, and the second‐hottest for North America and Asia. The hot summer concurred with a triple‐dip La Niña in the tropical Pacific. Given the extremity of the hot summer in East Asia in 2022, in this work, we examine the associated atmospheric circulation and assess the real‐time predictions from the North American Multimodel Ensemble (NMME). Also, we identify the contributions of long‐term warming trends, sea surface temperature (SST) forcing, and an atmospheric feedback to the hot summer. The hot summer in East Asia in 2022 is due to the extremely strong and westward expanded western Pacific subtropical high. That leads to cloud cover reduction and increases in net downward shortwave radiation at the surface, and further strengthens the positive surface air temperature (SAT) anomalies. In contrast, the seasonal‐interannual variation of SST has a minor impact. Thus, the hot summer is mainly associated with the long‐term trend and amplified by the positive feedback among the SAT, cloud cover, and net downward shortwave radiation. NMME with the initial conditions in May 2022 predicts positive SAT anomalies in most regions of East Asia, but does not capture the observed spatial distribution pattern and amplitudes. The failure implies the challenge of state‐of‐the‐art climate models in predicting such extreme events. Plain Language Summary: In the context of global warming, the northern hemisphere experienced an extremely hot summer in 2022 with the hottest on record for Europe and China. The hot summer concurred with a triple‐dip La Niña in the tropical Pacific during 2020–2023. In this work, we examine the causes and assess the real‐time predictions and predictability of the hot summer in East Asia. The hot summer in 2022 is due to the extremely strong and westward expanded western Pacific subtropical high. For the averages in the main hot summer region in East Asia in 2022, the largest contribution is from the long‐term trend (∼50%), and for the rest 50%, half of them is from the feedback among atmospheric circulation‐surface air temperature‐cloud cover‐net downward shortwave radiation. In contrast, the seasonal‐interannual components of the global sea surface temperatures play a secondary role. Multi‐model ensemble with the initial conditions in May 2022 predicts positive surface air temperature anomalies in most regions of East Asia, especially in August. However, compared with the observations, both the spatial distribution pattern of surface air temperature anomalies and their amplitudes have distinguished biases in the North American Multimodel Ensemble predictions. The failure implies the challenge of state‐of‐the‐art climate models in predicting such extreme events. Key Points: The hot summer in East Asia in 2022 is due to the extremely strong and westward expanded western Pacific subtropical highThe hot summer is caused by the long‐term trend and amplified by positive feedback among the surface air temperature (SAT), cloud, and downward shortwave radiationNorth American Multi‐model Ensemble does not capture the observed spatial distribution pattern and amplitudes of SAT anomalies [ABSTRACT FROM AUTHOR]