Over the past year or so, a handful of scientists and policymakers have started—very, very delicately—broaching the topic of geo-engineering. The idea is that, if the world can't (or won't) cut its greenhouse-gas emissions quickly enough to prevent large temperature increases, then we may have to ponder other ways to manipulate the climate directly, in order to fend off dangerous global warming. "It's got to be looked at," said White House science adviser John Holdren back in April. "We don't have the luxury... of ruling any approach off the table." (After the inevitable press frenzy, Holdren clarified that the White House wasn't, for the time being, pursuing this course.)
Confusingly, though, the term "geo-engineering" now gets used for a variety of different things. It can mean, on the one hand, taking truly radical action, like dumping a bunch of iron in the ocean to spur the growth of carbon-chomping algae, or lacing the stratosphere with sulfate aerosols in order to blot out some of the sun's rays. Graeme Wood recently wrote a great piece in The Atlantic about these wild-eyed schemes, noting that many of them could have potentially vicious side-effects (pumping sulfur-dioxide into the air, for instance, could wreak havoc on global rainfall patterns and cause drought in places we don't want drought). It's notions like these that make many scientists so skittish about using the g-word.
But not all geo-engineering ideas are necessarily drastic. Earlier this week, a new study from the Institute of Mechanical Engineers in Britain laid out some more modest measures to cool the Earth, and most looked a lot less problematic. We could, for instance, paint all our roofs white, reflecting more of the sun's heat off the surface and reducing the temperature of our urban centers. That's a form of geo-engineering, and one that's less likely to have unforeseen side-effects than trying to dim the sky. (Though granted, white roofs, like many geoengineering schemes, don't directly take carbon out of the air, so they do little to prevent, say, ongoing ocean acidification.)
The report also touts new artificial trees under development that could potentially suck up carbon-dioxide from the atmosphere more efficiently than regular trees do. Planting 100,000 such trees on a 1,500-acre area, for instance, could in theory absorb all the carbon-dioxide currently produced by Britain's non-power sector. Likewise, engineers could stick tubes filled with algae on the side of all our buildings—the algae would absorb carbon-dioxide from the air and could then be collected, turned into charcoal, and buried underground, trapping the carbon for all eternity.
Now, the authors rightly warn that these schemes can't possibly be a substitute for reducing man-made greenhouse gases. We'd still have to do that as well. But look at the state of play right now. Most nations are proposing very slow, gradual cuts to their emissions. As I noted the other day, even the most energetic low-carbon plan currently being envisioned by China would make it extremely difficult to avert a risky 2°C rise. Yet we're already starting to see some fairly devastating effects of climate change, from bark-beetle invasions to faster-than-expected Arctic sea ice melt. We'd be crazy not to look at things like carbon-eating trees—even if only to help us buy time.
(Flickr photo credit: Gabriel_Paul)