根据短文回答 23～30 题。
Global Warming
1 Smoke is clouding our view of global warming, protecting the planet from perhaps three-quarters of the greenhouse (温室) effect. That might sound like good news, but experts say that as the cover diminishes in coming decades, we are. facing a dramatic increase of warming that could be two or even three times as great as official best guesses.
2 This was the dramatic conclusion reached last week at a workshop in Dahlem, Berlin, where top atmospheric scientists got together, including Nobel Prize winner Paul Crutzen and Swedish scientist Bert Bolin, former chairman of the UN's Intergovemmental Panel on Climate Change (IPCC).
3 IPCC scientists have suspected for a decade that aerosols (浮质) of smoke and other particles from burning rainforest, crop waste and fossil fuels are blocking sunlight and counteracting the warming effect of carbon dioxide (二氧化物) emissions. Until now, they reckoned that aerosols reduced greenhouse warming by perhaps a quarter, cutting increases by 0.2~C． So the 0.6~C of warming over the past century would have been 0.8~C without aerosols.
4 But the Berlin workshop concluded that the real figure is even higher--aerosols may have reduced global warming by as much as three-quarters, cutting increases by 1.8~C． If so, the good news is that aerosols have prevented the world getting almost two degrees warmer than it is now. But the bad news is that the climate system is much more sensitive to greenhouse gases than previously guessed.
5 As those gases are expected to continue accumulating in the atmosphere while aerosols stabilize or fall, that means 'dramatic consequences for estimates of future climate change', the scientists agreed in a draft report from the workshop.
第 23 题 Paragraph 2______________
A．Atmospheric Scientists
B．The Calculations Made at the Berlin Workshop
C．The Previous Calculations of the Effect of Aerosols
D．The Scientists'Agreement
E．The Authoritative Conclusion
F．Greenhouse Gases

A.
2
B.
3
C.2~C．
D.6~C
E.8~C
F.
4
G.8~C．
H.
5
I.Atmospheric
J.The
K.The
L.The
M.The
N.Greenhouse