At the moment, scientists agree that the world's climate 1) b warmer over the past 50 years, but they disagree about the causes. some believe that human activities 2) climate change. they argue that for 1,000 or 2,000 years before 1850, when the temperature was more or less stable. short warm or cold periods 4) during that time, but the climate the same level. however, since the industrial revolution, human beings 6) more and more fossil fuels, such as coal and oil. in 1800 the atmosphere 7) around 280 parts per million of carbon dioxide (co2). since then there 8) an increase of about 3 l%. this extra carbon dioxide 9) the world's temperature because of the greenhouse effect. other scientists disagree that human activities over the past 50 years 10) global warming. they point out that volcanoes and other natural processes 11) co2 into the atmosphere, and that human activity12) a rise in co2 of only three per cent. in 1999, 156 countries13) the kyoto protocol, part of a united nations agreement on climate change, which14) into force in 2005.they 15) to reduce their emissions of co2 and other greenhouse gases, although so far, some countries, such as the usa and australia, action. ответы: 1. a became b has become 2. a caused b have caused 3. a began b have begun 4. a occurred b have occurred 5. a returned b has returned 6. a burned b have burned 7. a contained b has contained 8. a was b has been 9. a raised b has raised 10. a caused b have caused 11. a always released b have always released 12. a contributed b has contributed 13. a signed b have signed 14. a came b has come 15. a agreed b have agreed 16. a did not take b have not taken
2b
3a
4a
5a
6b
7a
8b
9b
10b
11b
12b
13a
14a
15a
16b