The increase in temperature due to the trapping of energy by ozone,$CO_2$,and water vapour is known as:

The given diagram represents the greenhouse effect.
$I.$ Greenhouse gases absorb infrared radiation from the earth. The absorbed radiations are again emitted towards the earth's surface,heating it up.
$II.$ $CO_{2}, CH_{4}, CFCs$ and $N_{2}O$ are the gases responsible for the greenhouse effect.
$III.$ An increase in the level of greenhouse gases results in considerable heating of the earth,leading to global warming.
Which of the statements given above are correct?

The greenhouse effect is caused by . . . . . . .

The two gases making the highest relative contribution to the greenhouse effect are:

If there is no greenhouse effect,the average temperature at the surface of the Earth would have been: (in $^{\circ} C$)

Which one of the following is $NOT$ caused by global warming?