Science Channel - InSCIder

26 Jun

Should we alter the color of the sky?

Blue Skies?For the fact-based among us, it's tempting to poke fun at those conspiracy mavens on the web who have long claimed that contrails -- that is, the thin streams of vapor left behind in the atmosphere by jet aircraft -- are actually evidence of a clandestine effort by the New World Order to modify our planet's weather. But as Nirvana's Kurt Cobain once noted," just because you're paranoid, don't mean they're not after you." We may want to walk back the smugness a bit. As it turns out, some visionaries actually are discussing the possibility of altering the Earth's atmosphere, as a last-ditch tactic to combat rapidly escalating climate change -- even though a newly-published scientific paper shows that it might banish the brilliant blueness from our skies and turn them vanilla-colored during the day. (Quite possibly, the sky also would be eerily blood-red at sunset as well, but we'll get to that later.)

The most logical way to slow rising global temperatures, of course, would be for humans to reduce the amount of carbon dioxide and other greenhouse gases that they pump into the atmosphere. Good luck with that, though. And that's why advocates of geoengineering, the nomenclature for massive planetary-scale projects to alter the environment, have suggested more radical big fixes. One proposal that's gained some traction is the notion of imitating the cooling effect of massive volcanic eruptions, by deliberately injecting sulphate aerosols into the upper atmosphere to reflect some of the sun's energy away from the Earth. As this ArsTechnica article explains:

Fleets of small jet aircraft could fly into the lower stratosphere several times a day and release sulfur gas to produce planet-cooling sulfate aerosols. Or giant balloons made out of plastic could be equipped with long hoses and used to pump sulfur gas upwards into the atmosphere.

Just how well the manmade volcano effect would work is a matter of debate. In a study published in 2010 in Nature Geoscience, Carnegie-Mellon University climate scientist Kate Ricke and colleagues used climate modelling to look at the potential impact of such a solar radiation-blocking strategy. They found that its effects might be extremely uneven across the globe, and cause destructive weather changes in some places. As a news article in Nature elaborated:

For example, Ricke says, her study found that levels of sulphate that kept China closest to its baseline climate were so high that they made India cold and wet. Those that were best for India caused China to overheat.

Granted, Ricke and colleagues also found that both countries fared better in terms of climate alteration that they would have under a do-nothing scenario. But they also found that over time, the simulated volcano effect would result in increasingly uneven effects. It also would cause a global decrease in rainfall, which I would fear might pose long-term risks to the planet's food production.

In the short term, we'd also have to get used to another strange effect of spewing sulphate aerosol into the upper atmosphere: no more brilliant blue skies. Instead, as this recent press release by the Carnegie Institution for Science details,

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.

Why would this happen? As this New Scientist article explains, the color of the sky comes from the scattering of sunlight by molecules in the atmosphere, which act as a filter. Right now, the frequencies that produce the color blue are what gets to our eyes. Large quantities of bigger sulphate aerosol particles, however, would scatter red wavelengths more strongly, balacing the blue and making the sky brighter and whiter.

The Scream

While sky-whitening is the effect that's been causing a buzz across the web, that effect would be seen only during the day. Pumping sulphate aerosols into the upper atmosphere also would alter sunsets, making them more intensely red and creating a strange afterglow. I'm not sure if the effect would be quite as overwhelming as the eerie end-of-the-day redness of European skies  caused by an eruption on the Indonesian island of Krakatoa in 1883--which, in turn, inspired the lurid bloody sky of  Edvard Munch's painting "The Scream." I'm feeling a little enervated, just imagining what the psychological effect upon vast numbers of people across the world might be. Cree-py.

So what do you think about geoengineering and altering the sky to counteract global warming? Express your opinion below.

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