it could make the Earth warmer than usual. Even a little extra warming may cause problems for humans， plants， and animals.

　　Section_ⅠWarm­up__&_Lesson_1_-_Pre­reading

　　Can we take the heat?

　　In the last few decades①， scientists have reached consensus② and reported that human beings are causing changes in the Earth's climate - something previously ③seen as beyond our control④. They claim⑤ that in the last 50 years, gases pumped into⑥ the Earth's atmosphere by the factories and vehicles have been speeding up⑦ the process of global warming and affecting our climate. Looking ahead⑧， scientists believe that global warming could be one of the biggest environmental problems facing the 21st century⑨. But what exactly is global warming, why is it seen as\s\up1(10(10) a danger⑪， and how is it relevant⑫ to our lives?

　　Global warming refers to⑬ an average⑭ increase in the Earth's temperature that, in turn⑮， leads to⑯ climate change⑰. Scientists found that the temperature of the Earth is controlled by greenhouse gases such as carbon dioxide which trap heat from the sun in the Earth's atmosphere⑱. Without these naturally occurring gases, the sun's rays⑲ would bounce⑳ back into space leaving the Earth cold and impossible to live on\s\up1(21(21). When the presence of these gases in the atmosphere increases, however, more heat is trapped and the Earth's temperature rises.

　　①in the last/past few decades/years/months/days此类短语，通常与现在完成时连用。in也可换成over或during。本段和第三段均含有此类结构。

　　②consensus/kən'sensəs/n.一致的意见

　　③seen as beyond our control是过去分词短语作定语，修饰something。

　　④beyond one's control 超出......的控制，不受......的控制

　　⑤claim/kleIm/vt.声称　⑥pump into注入

　　⑦speed up 加快速度　 ⑧look ahead 展望未来

　　⑨现在分词短语facing the 21st century作后置定语，修饰the biggest environmental problems。

　　⑩be seen as 被看作

⑪danger n．[C]"危险的人，危险的事物"。在文中为抽象名词具体化。