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 records3)___, the temperature was more or less stable. Short warm or cold periods 4) ___ during that time, but the climate always5)___to 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,16)___any 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