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From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.

A researcher publishing in the journal Science this week says he has a way to save the earth from global warming - for a while, at least. The idea is to block out some sunlight, more specifically to do what volcanoes do, inject clouds of material into the stratosphere. That would create a thin haze and deflect some of the sun's rays away from the earth.

NPR's David Kestenbaum reports.

DAVID KESTENBAUM: The general idea has been around for decades and for decades it has made people uncomfortable. Tom Wigley is the author of the new paper and his perspective is look, we're already doing something wrong-headed, pumping greenhouse gases into the atmosphere, putting the planet at major risk.

Mr. TOM WIGLEY (National Center for Atmospheric Research): I think the problem is sufficiently serious that we may well have to do something that at face value seems a little odd.

KESTENBAUM: Tell me how you came up with this crazy idea.

Mr. WIGLEY: Hey, don't call this a crazy idea. This is a very serious idea. And I'm serious when I say that.

KESTENBAUM: Wigley is a senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, and his proposal is to inject relatively small amounts of material into the stratosphere, not as a permanent solution as some others have suggested, but just to buy time until greenhouse gas emissions can be brought under control.

The basic principle is well established. In 1991, Mount Pinatubo in the Philippines erupted. It put a thin haze of particles into the stratosphere that eventually circled the globe. Estimates are the haze cooled the earth the following year by about 1 degree Celsius, all by deflecting a tiny fraction of the sun's light. Wigley ran some computer models on his laptop.

Mr. WIGLEY: What I'm suggesting is, sort of amounts to having a Pinatubo every couple of years. That would be enough to offset most of the warming over the next hundred years due to greenhouse gas concentration increases - not all of it, but most of it.

KESTENBAUM: Over the years, other researchers have also done serious calculations. Ken Caldeira is a climate scientist with the Carnegie Institution at Stanford University.

Mr. KEN CALDEIRA (Carnegie Institution, Stanford University): Several idea of how you get the aerosols into the stratosphere. One is that you could essentially shoot them out of big guns into the stratosphere. You could fly them up in airplanes. There's also the idea of essentially making a huge smokestack, not out of rigid material, but more or less a tube that might be suspended with balloons.

KESTENBAUM: The cost would be in the billions, he says, but it's probably doable and in the short term, much cheaper than switching away from fossil fuels. Caldeira says there are other big ideas for how to offset the effects of global warming. He works on them, but he kind of hates them. He thinks trying to engineer the climate is a terrible idea.

Pumping material into the stratosphere is at best a Band-Aid, he says. CO2, the major greenhouse gas, would still build up, making the oceans more acidic, threatening coral reefs and possibly life at the bottom of the food chain.

Mr. CALDEIRA: I think it's a step down the path towards global environmental destruction.

KESTENBAUM: And injecting particles into the stratosphere could also do some harm. They could slow the healing of the ozone layer and they'd make a little acid rain.

Mr. CALDEIRA: The things that we can think of, as bad as they are, are the things I'm least afraid of. I'm more afraid of the things that we can't think of.

KESTENBAUM: But Tom Wigley in his paper says there's good evidence this is safe. He points to the Pinatubo eruption as an example, and you could turn it off if trouble arose. These are the sort of big ideas scientists like to talk about at the hotel bar during conferences, but these days they are the subject of conferences. Richard Alley is a climate researcher at Penn State University.

Mr. RICHARD ALLEY (Penn State University): The first response is man, this is crazy. But I think Wigley's right, I think the other people thinking about this are right, that we have a responsibility to look at all the possibilities, and once we do that, then wise people can make wise decisions.

KESTENBAUM: Ken Caldeira at Stanford says many of his colleagues are now convinced that some big project like this is inevitable.

David Kestenbaum, NPR News.

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