Hansen cautioned that greenhouse gases

Hansencautionedthatgreenhousegases________

producesmuchmoreglobalwarmingthanacarbon-dioxideforcingofthesamemagnitude

contr ibutedto25percentofobservedglobalwarming

winterandspring

thewarmingeffectsincrease

stillsurpasssootwarmingtheworld'sclimateduringthelastcentury

canbeseenmostlyintheNorthernHemisphere

答案及解析：本题定位到第六段汉森提醒大家注意的话,温室气体仍是导致全球变暖的最主要因素。