B13

'Greenhouse affect' is actually a natural feature of our atmosphere

 NATURE

B14

without which life on our planet would be impossible.

 POSSIBLE

B15

Certain atmospheric gases work as a kind of blanket, keeping the Earth warm. The amount of these 'greenhouse' gases used to be more or less the same for centuries. But the industrial revolution broke this balance.

 INDUSTRY

B16

Because of heavy industry and other human activities the amounts of CO₂ and other gases have increased by 30%.

 ACTIVE

B17

Climate experts predict that by 2050 the global average temperature will rise by 2-3 degrees.

 GLOBE

B18

It doesn't seem much. Remember, however, that the difference between the average global temperatures now and the last ice age (20,000 years ago) is only 6 to 8 degrees.

 DIFFER