Global warming means a …………… in average effective temperature near the earth’s surface due to an …………… in the amount of greenhouse gases in its atmosphere.

1. decrease, increase
2. decreases, decrease
3. increase, decrease
4. increase, increase

The global warming has resulted in —

1. the increase in yield of crops
2. the decrease in sea levels
3. the decrease in human deaths
4. the increase in sea levels.

What do you mean by green house effect?

Name three green house gases.