Aerosol geoengineering could make sky white instead of blue

Some scientists advocate pumping aerosols into the atmosphere to counter global warming by reflecting solar energy away.

But according to Carnegie Institution scientists, the price we’d have to pay is the loss of the Earth’s blue skies. Blocking two percent of the sun’s light, they say, would make the sky three to five times brighter, and a much, much paler color.

The idea behind pumping aerosols into the atmosphere is to mimic the cooling effect of large volcanic eruptions, which cool the planet by creating lots of small particles in the stratosphere that scatter sunlight back to space.

But by using models, the team found that, depending on the size of the particles, the sky would whiten during the day and sunsets would have afterglows.

“These results give people one more thing to consider before deciding whether we really want to go down this road,” says Carnegie’s Ben Kravitz. “Although our study did not address the potential psychological impact of these changes to the sky, they are important to consider as well.”

There are other, larger, environmental implications too. Because plants grow more efficiently under diffuse light conditions, global photosynthetic activity could increase, pulling more  carbon dioxide out of the atmosphere.

On the other hand, the effectiveness of solar power could be diminished, as less sunlight would reach solar-power generators.

“I hope that we never get to the point where people feel the need to spray aerosols in the sky to offset rampant global warming,” says scientist Ken Caldeira.

“This is one study where I am not eager to have our predictions proven right by a global stratospheric aerosol layer in the real world.”