When it's cloudy, the direct beam drops to nearly zero, but there can still be a lot of scattered sunlight. (green.blogs.nytimes.com)
Particles spewed high into the atmosphere by those eruptions scattered sunlight back into space, thus cooling Earth substantially, the researchers explain. (sciencemag.org)
This image shows atomic hydrogen scattering sunlight in the upper atmosphere of Mars, as seen by the Imaging Ultraviolet Spectrograph on NASA's Mars Atmosphere and Volatile Evolution mission. (sciencedaily.com)