四、長篇閱讀(第 41–50 題)
Over time periods of thousands of years, the Earth goes through a natural cycle of warmer
and colder periods, driven by changes in heat coming from the Sun. Professor William
Ruddiman has now calculated that if the Earth had followed its natural cycle over the last ten
thousand years, it ought to have got steadily colder. It hasn’t because, he believes, human
activities have been keeping the temperature steady.
“What should have happened with the natural climate is it should have cooled
substantially. And instead humans just started adding greenhouse gases to the atmosphere at a
rate which cancelled most, but not quite all, of that natural cooling; and so it’s a combination of
a natural cooling mostly cancelled by a human warming.”
Our ancestors started adding the greenhouse gas carbon dioxide principally by cutting
down trees for farming; whereas methane production started with wet farming of rice. Professor
Ruddiman believes this ten-thousand year warming added almost a degree Celsius to the
average temperature.
【題組】41.What is the most appropriate topic of this essay?
(A) Climate Change
(B) Natural Climate
(C) Greenhouse Gas
(D) Wet Farming
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