1-1. 다음 글의 주제로 가장 적절한 것은?

Some pessimistic scientists believe that climate change on Earth has already passed the ‘tipping point’ beyond which it is not possible to stop the slide into global meltdown. But other groups of scientists think that even if the tipping point has been and gone there might still be hope for the planet in the form of geo-engineering, which is superscale design-and-build work that could reverse the effects of climate change. The ideas put forward include sending giant sunshades into space to block out some of the Sun’s light; building a network of industrial plants around the globe that would suck in carbon dioxide, compress it into liquid, and then pump it underground; and tipping gallons of fertilizer into the oceans to encourage the growth of marine plant life to absorb carbon dioxide from the air by photosynthesis.

① ways to control air pollution

② important functions of carbon dioxide

③ how geo-engineering are formed

④ ways to protect global warming

⑤ severe damages caused by carbon dioxide