31 May 2012: Geoengineering Scheme Could
Make Sky Brighter and Whiter, Study Says

Spraying aerosols into the atmosphere, one of the so-called geoengineering schemes often proposed as a way to counteract global warming, would also make the daytime sky significantly brighter and whiter, according to a new study. Using sophisticated models, researchers estimated that a 2-percent reduction in the sun’s light — which would be approximately enough to offset warming in the case of a doubling of atmospheric concentrations of carbon dioxide — would have the side-effect of making the sky three to five times brighter. Depending on the size of the sulfate-based aerosol particles, the sky would become whiter during the day and trigger the types of vivid sunsets often seen following large volcanic eruptions. While the sky would still be blue, the researchers say, it would be a lighter shade than most people are used to — and more similar to the sky colors seen over urban areas. “These results give people one more thing to consider before deciding whether we really want to go down that road,” said Ben Kravitz, a researcher at the Carnegie Institution for Science and co-author of the study, published in the journal Geophysical Research Letters.