A Sunshade（遮阳伞）for the Planet

Even with the bestwill in the world,reducing our carbon emissions is not going to prevent globalwarming. It has become clear that even if we take the most strong measures

to controlemissions, the uncertainties in our climate models still leave open thepossibility of extreme warming and rises in sea level. At the sametime,resistance by

governments andspecial interest groups makes it quite possible that the actions suggested byclimate scientists might not be implemented soon enough.

Fortunately,if theworst comes to the worst,scientists still have a few tricks up their sleeves.For the most part they have strongly resisted discussing these options for fearof

inviting a sense ofcomplacency that might thwart efforts to tackle the root of the problem. Untilnow,that is a growing number of researchers are taking a fresh look at large-

scale"geoengineering"projectsthat might be used to counteract global warming."I use the analogy ofmethadone,"says Stephen Schneider,a climate researcher at Stanford

University in California who was amongthe first to draw attention to global warming."If you have a heroinaddict,the correct treatment is hospitalization,and a long rehab.

But if theyabsolutely refuse,methadone is better than heroin."

Basically the ideais to apply"sunscreen"to the whole planet. One astronomer has come upwith a radical plan to cool Earth:launch trillions of feather-light discs into

space,where theywould form a vast cloud that would block the sun's rays.It's controversial,butrecent studies suggest there are ways to deflect just enough of the sunlight

reaching the Earth'ssurface to counteract the warming produced by the greenhouse effect. Globalclimate models show that blocking just 8 percent of the incident energy in

the sun's rays wouldcancel out the warming effects produced by a doubling of greenhouse gases inthe atmosphere.That could be crucial,because even the most severe

emissions controlmeasures being proposed would leave us with a doubling of carbon dioxide by theend of this century,and that would last for at least a century more.Scientists resisttalking about their options because they don't want people to______.

A.know what they aredoing

B.feel their effortsare useless

C.think the problemhas been solved

D.see the real problem