【全国英语等级考试三级】Unit 4 天气与气候—passage (3/4)

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Unit 4 Weather and Climate 天气与气候
passage (3/4)
        Hints:
        Northern Hemisphere
        Arctic Ocean
4-8
       
Increased agriculture, deforestation, landfills, industrial production, and mining also contribute a significant share of emissions. In 1997, the United States emitted about 1/5 of total global greenhouse gases. The 20th century's ten warmest years all occurred in the last 15 years of the century. Of these, 1998 was the warmest year on record. The snow covers in the Northern Hemisphere and floating ice in the Arctic Ocean have decreased. Globally, sea level has risen 4-8 inches over the past century. Worldwide precipitation over land has increased by about 1%. The frequency of extreme rainfall events has increased throughout much of the United States. Increasing concentrations of greenhouse gases are likely to accelerate the rate of climate change.