Unit 4 Weather and Climate 天气与气候
passage (1/4)

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National Academy of Sciences

Fahrenheit

 

According to the National Academy of Sciences, the Earth's surface temperature has risen by about one degree Fahrenheit in the past century, with accelerated warming during the past two decades. There is new and stronger evidence that most of the warming over the last 50 years is attributable to human activities. Human activities have altered the chemical composition of the atmosphere through the buildup of greenhouse gases - primarily carbon dioxide, methane, and nitrous oxide. Energy from the sun drives the earth's weather and climate, and heats the earth's surface. In turn, the earth radiates energy back into space. Atmospheric greenhouse gases - water vapor, carbon dioxide, and other gases trap some of the outgoing energy, retaining heat somewhat like the glass panels of a greenhouse.