uo;s energy and warmth than an icy, white background．Dark-colored black carbon，or soot，absorbs sunlight，while lighter colored ice reflects sunlight．
3 Soot in areas with snow and ice may play all important role in climate change．Als0，if snow and ice covered areas begin melting。the warming effect increases，as the soot becomes more concentrated on the snow surface．“This provides a positive feedback，as glaciers and ice sheet smelt,they tend to get even dirtier,” said Dr．James Hansen，a researcher at NASA's Goddard Institute for Space Studies，NewYork．
4 Hansen found soot’s effect on snow albedo(solar energy reflected back to space)，which may be contributing to trends toward early springs in the Northern Hemisphere，such as thinning Arctic sea ice，melting glaciers and permafrost．Soot also is believed to play a role in changes in the atmosphere above the oceans and land．
5 “Black carbon reduces the amount of energy reflected by snow back into space，thus heating the snow surface more than if there were no black carbon~，”Hansen said．Soot’s increased absorption of solar energy is especially effective in warming the world’s climate. “This forcing is unusually effective，causing twice as much global warming as a carbon．dioxide forcing of the same magnitude，”Hansen noted．
6 Hansen cautioned．although the role of soot in altering global climate is substantial，it does not alter the fact that greenhouse gases are the primary cause of climate warming during the past century．Such gases are expected to be the largest climate forcing f10r也e rest of this century．
7 The researchers found that observed warming in the Northern Hemisphere was 1arge in the winter and spring at middle and high latitudes．These observations were consistent with the researchers’ climate model simulations，which showed some of the largest warming effects occurred when there were heavy snow cover and sufficient sunlight．

词汇：
soot n．煤烟，煤灰
emission n．释放，散发，排放
simulation v．模拟
latitude n．纬度
glacier n．冰川，冰河
albedo n．反照率
permafrost n．永冻层
forcing n．温室作用
dioxide n．二氧化物
magnitude n．量，大小

练习：
1．Paragraph 3____________
2．Paragraph 4____________
3．Paragraph 6____________
4．Paragraph 7____________


5．In the twentieth century，soot____________
6．Hansen cautioned that greenhouse gases____________
7. Black soot covered snow and ice____________
8．A soot forcing is unusually effective，which____________


第四部分：阅读理解（每题3分，共45分）
下面有3篇短文，每篇短文后有5道题，每道题后面有4个选项。请仔细阅读短文并根据短文回答其后面的问题，从4个选项中选择1个最佳答案涂在答题卡相应的位置上。

第1篇

Medical Journals

Medical journals are publications that report medical information to physicians and other health professionals．
In the past，these journals were available only in print．With the