A soot forcing is unusually effective, which

Asootforcingisunusuallyeffective,which_________

producesmuchmoreglobalwarmingthanacarbon-dioxideforcingofthesamemagnitude

contr ibutedto25percentofobservedglobalwarming

winterandspring

thewarmingeffectsincrease

stillsurpasssootwarmingtheworld'sclimateduringthelastcentury

canbeseenmostlyintheNorthernHemisphere

答案及解析：本题定位到第五段最后一句话非常清楚,答案也很明显。