Impact of changes in diffuse radiation on the global land carbon sink

Increased exposure to solar radiation generally increases plant photosynthesis, but not all forms of radiation are equally effective. In particular, field studies have demonstrated that a given amount of diffuse radiation leads to more fixed carbon than direct radiation. Mercado et al. use the HadGEM2-A general circulation model to simulate the effect of late twentieth century 'global dimming' and associated increases in the diffuse radiation fraction on global carbon storage. They find that increases in diffuse radiation enhanced the terrestrial carbon sink by about 25%. Paradoxically, reducing anthropogenic pollution in the future would reduce this diffuse radiation effect, thereby creating a positive feedback to global warming.