Fig. 1: A view of the Chilean Sc deck from the MODIS⁴¹ satellite instrument.

The colour scale indicates cloud droplet effective radius. a,b, Grey boxes show the location of emissions (a) and where they are advected to with the wind (b). There are visible ship tracks in darker colours, most of which are well collocated to advected ship emissions. MODIS Aqua on 6 August 2018. c, The same region but for a day without visible ship tracks, even though there are ships. d, Advected emission locations and in addition the counterfactual retrieval boxes to either side of them (yellow boxes). MODIS Aqua on 14 September 2019, selected ships. Map of the retrieval location from cartopy⁴².