Piyu Ke, Philippe Ciais, Yitong Yao, Stephen Sitch, Wei Li, Yidi Xu, Xiaomeng Du, Xiaofan Gui, Ana Bastos, Sönke Zaehle, Ben Poulter, Thomas Colligan, Auke M van der Woude, Wouter Peters, Zhu Liu, Zhe Jin, Xiangjun Tian, Yilong Wang, Junjie Liu, Sudhanshu Pandey, Chris O'Dell, Jiang Bian, Chuanlong Zhou, John B Miller, Xin Lan, Jefferson Goncalves De Souza, Michael O'Sullivan, Pierre Friedlingstein, Guido R van der Werf, Glen P Peters, Shilong Piao, Frédéric Chevallier
El Niño droughts can weaken tropical land carbon uptake and accelerate atmospheric CO2 growth. We updated the low-latency global CO2 budget through June 2024 using near-real-time fossil emissions, four dynamic global vegetation models (DGVMs), ocean carbon emulators, and three OCO-2 atmospheric inversions. From July 2023 to June 2024, atmospheric CO2 grew by 3.66 ± 0.09 ppm yr-1, the highest July-to-July rate since 1979; after detrending, the anomaly was 1.1 ppm yr-1, comparable to previous major El Niño events. The anomaly was mainly driven by a 2.24 GtC yr-1 weakening of the net land sink, partly offset by 0.38 GtC yr-1 stronger ocean uptake. The tropics accounted for 97.5% of the land anomaly, led by the Amazon, central Africa, and Southeast Asia. This update shows how recent El Niño droughts drove the high CO2 growth rate through mid-2024 and how low-latency budgets can track carbon cycle extremes.