As new regulations clean up shipping fuels in order to improve air quality in coastal regions, that brightening effect will be reduced, adding to the world's warming in a sort of inadvertent reverse geoengineering.

ECONOMIST: Geoengineering

"If it is true that the mechanism is all about rays enhancing diffuse radiation, it would mean that 'global dimming' and 'global brightening' would have a big effect on tree growth and therefore on the absorption of carbon dioxide, " warns Ms Dengel.

BBC: Earth News - Cosmic pattern to UK tree growth