Greenland's melting ice sheet
Greenland's melting ice sheet - 


SCOTT JAGOW: Most of the ideas for mitigating global warming are about changing our energy behaviors, but NASA has some solutions in mind as well. Sam Eaton reports from our Sustainability Desk.

SAM EATON: They sound like something out of a sci-fi movie: unmanned fleets of ships blasting cloud-forming water droplets into the air, trillions of miniature reflectors in space that act as a giant sunshade.

Ken Caldeira with the Carnegie Institution says the growing scientific interest in these planet-sized solutions is simple, their pocket-sized budgets.

Cheapest of all, he says, is a small hose reaching into the stratosphere that could release enough tiny particles to cool the earth.

KEN CALDEIRA: It's thought that to keep that going year round might cost a couple of hundred million dollars a year. Whereas the cost of transforming our energy system's thought to cost hundreds of billions of dollars a year.

But Caldeira says the risk is that these technologies could be seen as an excuse for inaction on reducing greenhouse gas emissions.

In Los Angeles, I'm Sam Eaton for Marketplace.

Follow Sam Eaton at @eatonsam