四川自考网> 试题题库列表页> Task 221. In the twentieth century, soot          22. If snow and ice covered areas begin melting,           23. A soot forcing is unusually effective, which          24. Hansen cautioned that greenhouse gases          25. Warming in the Northern Hemisphere was large in at middle and high latitudes.           A. produces much more global warming than a carbon-dioxide forcing of the same magnitudeB. contributed to 25 percent of observed global warmingC. winter and springD. the warming effects increaseE. still surpass soot in warming the world's climate during the last centuryF. can be seen mostly in the Northern Hemisphere