Earth now is dominated by both biogeophysical and anthropogenic processes, as represented in these two images from a simulation of aerosols. Dust (red) from the Sahara sweeps west across the Atlantic Ocean. Sea salt (blue) rises into the atmosphere from winds over the North Atlantic and from a tropical cyclone in the Indian Ocean. Organic and black carbon (green) from biomass burning is notable over the Amazon and Southeast Asia. Plumes of sulfate (white) from fossil fuel burning are...