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...