Similar to clouds, volcanic eruptions increase the proportion of diffuse light reaching Earth's surface. As
Farquhar and Roderick
show in their Perspective, this change in the geometry (rather than intensity) of light can have a profound influence on photosynthesis
and the carbon cycle. They highlight the research article by
., who have measured changes in net COexchange following the eruption of Mt. Pinatubo in 1991. Volcanoes, pollution, and greenhouse
gases may all increase diffuse light, with important consequences for Earth's carbon cycle and climate.