Ship tracks—bright, linear clouds trailing ocean-going ships—are striking manifestations of cloud adjustment in response to inadvertent aerosol perturbations from shipping emissions. Their radiative characteristics, contrasted with surrounding unperturbed scenes, offer invaluable insights into aerosol–cloud–radiation interactions. In 2020, new fuel regulations were implemented in the shipping sector, limiting sulfur emissions from ships across the world’s oceans. While reducing this atmospheric pollutant improves air quality, the change has complex and unintended consequences for global warming.

The Science In this work, I trained ensembles of neural networks to examine how reduced pollution from shipping affects cloud properties and climate. The results reveal that while the IMO2020 regulation brings significant environmental and public health benefits, it also produces a global warming effect of approximately 0.1 W m−2, equivalent to about 3.5 years of CO2 warming. We concluded that even this substantial, abrupt radiative forcing is challenging to detect, underscoring the difficulty of observing real-world cloud adjustments against natural cloud variability. Regionally, detectability is higher for the southeastern Atlantic stratocumulus deck.

The Impact This study raises concerns that future reductions in aerosol emissions will accelerate warming and that proposed deliberate aerosol perturbations such as marine cloud brightening will need to be substantial in order to overcome the low detectability.

  • J. Zhang, Y.-S. Chen, E. Gryspeerdt, T. Yamaguchi, and G. Feingold (2025): Radiative forcing from the 2020 shipping fuel regulation is large but hard to detect. Commun. Earth Environ., 6(18), 1–11. doi:10.1038/s43247-024-01911-9