A Climate Cure's Dark Side

Article excerpt

Byline: Sharon Begley

It sounded like a panacea for climate change: "geo-engineering" the atmosphere to block some sunlight and counter global warming. Now scientists scrutinizing the approach say it could produce dangerous cascade effects, severely disrupting weather and agriculture--and might fail to block the worst of the greenhouse effects anyway.

Two prominent climate scientists raised the possibility of geo-engineering in 2006, and it's been invoked as the world's emergency escape hatch ever since--a quick fix to stabilize or even reverse the heating of the planet. It would head off worsening heat waves, droughts, and rising sea levels. The estimated price is right, too. A 2009 analysis found that geo-engineering would cost only $2 billion or so a year, chump change compared with converting from CO2-producing coal, oil, and natural gas to wind, solar, nuclear, and biofuels.

But further study shows worrying pitfalls, according to a series of research papers that will appear in the next issue of Atmospheric Science Letters. The greatest threat is to Asian monsoons, which are driven by the temperature difference between warm land and cooler seas. In one scheme, a fleet of jets would crisscross the planet releasing five megatons of sulfur dioxide gas every year. The gas would mix with water in the stratosphere to form minuscule particles called sulfate aerosols, which scatter incoming sunlight back to space before it warms the atmosphere or ground. (That's also how volcanic eruptions cool the planet.)

But oceans are harder to cool than land. As the sun effectively dims, warmer land cools faster than cooler oceans, explains meteorologist Alan Robock of Rutgers University. Shrinking that land-sea temperature gap would enfeeble the summer monsoons over Asia and Africa, a possible catastrophe for the billions who depend on that rain for their crops.

Perversely, geo-engineering might also reinforce some of the worst consequences of global warming, says climate modeler Olivier Boucher of the British Met Office, the U. …