Geoengineering for Global Warming

One idea for fighting global warming is to increase the amount of aerosols in the atmosphere, scattering incoming solar energy away from Earth\'s surface. But scientists theorize that this solar geoengineering could have a side effect of whitening the sky during the day. New research from Carnegie\'s Ben Kravitz and Ken Caldeira indicates that blocking 2% of the sun\'s light would make the sky three-to-five times brighter, as well as whiter. Their work is published June 1st in Geophysical Research Letters, a journal of the American Geophysical Union. Carbon dioxide emissions from the burning of coal, oil, and gas have been increasing over the past decades, causing Earth to get hotter and hotter. Large volcanic eruptions cool the planet by creating lots of small particles in the stratosphere, but the particles fall out within a couple of years, and the planet heats back up. The idea behind solar geoengineering is to constantly replenish a layer of small particles in the stratosphere, mimicking this volcanic aftermath and scattering sunlight back to space. Using advanced models, Kravitz and Caldeira -- along with Douglas MacMartin from the California Institute of Technology -- examined changes to sky color and brightness from using sulfate-based aerosols in this way. They found that, depending on the size of the particles, the sky would whiten during the day and sunsets would have afterglows. Their models predict that the sky would still be blue, but it would be a lighter shade than what most people are used to looking at now. The research team\'s work shows that skies everywhere could look like those over urban areas in a world with this type of geoengineering taking place. In urban areas, the sky often looks hazy and white.