Black carbon particles, commonly called soot, are dark and light-absorbing and therefore warm the climate. Soot comes from combustion of fossil and biofuels, especially burning of diesel, coal and wood. Due to its warming effects, reduction of soot could help cool climate. However, soot absorption also affects cloud distributions and the verdict on how the clouds change is unclear. Because clouds mostly cool the climate, the possibility that soot absorption could increase cloud cover needs to be considered.
Turns out the net warming effect from absorbing aerosols (AAs) such as black carbon (BC) or dust is more complicated than previously realized. That’s the conclusion of a major review of the literature on the “semi-direct effects of absorbing aerosols,” in Atmospheric Chemistry and Physics, “Black carbon absorption effects on cloud cover: Review and synthesis,” by two NASA Goddard Institute for Space Studies.
And that means reducing BC may not be the silver bullet solution many thought. The study concludes that in some climate model studies, “the cooling effect of BC due to cloud changes is strong enough to essentially cancel the warming direct effects.”