Our understanding of the impact of aerosol particles on deep-convective clouds is still incomplete. Earlier research found increased lightning above shipping lanes and hypothesized that the ship emissions support the development of deep-convective cloud systems. The present study investigates the effect of a sevenfold reduction in sulphur content of shipping fuel, implemented following the International Marine Organisation 2020 regulation. A significant decrease in lightning activity is found over shipping lanes in combination with a reduction of both the concentration and the size of the emitted particles, providing further evidence of a strong connection between shipping missions, deep-convective cloud development, and lightning activity. This highlights the need to resolve the still unclear acting mechanisms.

Effusive, long-lasting volcanic eruptions impact climate through emission of gases and subsequent production of aerosols. Although previous studies have shown that the sulphate aerosol produced by these eruptions cools Earth's climate, this Earth system modelling study shows that high-latitude effusive eruptions can cause Arctic warming during the fall and wintertime. This warming effect is caused by the enhancement of downward longwave radiation from very optically thin clouds. The results have implications for our understanding of future Arctic climate change as well as any efforts to deliberately modify the climate through solar radiation management.