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  3. In even the bleakest climate change scenarios for the end of this century, sc

In even the bleakest climate change scenarios for the end of this century, sc

游客2023-12-22  56
问题    In even the bleakest climate change scenarios for the end of this century, science has offered hope that global warming would eventually slow down. But a new study published Monday snuffs out such hope, projecting temperatures that rise with carbon emissions until the last drops of oil and lumps of coal are used up.
   Global temperatures will increase on average by 8°C(14. 4°F)over pre-industrial levels by 2300 if all of Earth’s fossil fuel resources are burned, adding five trillion metric tons of carbon to the atmosphere, according to the research by Canadian scientists published in Nature Climate Change. In the Arctic, average temperatures would rise by 17°C(30. 6 °F).
   Those conclusions are several degrees warmer than previous studies have projected. If these temperatures do become reality, greenhouse gases would transform Earth into a place where food is scarce, parts of the world are uninhabitable for humans, and many species of animals and plants are wiped out, experts say. "It would be as unrecognizable to us as a fully glaciated world," says Myles Allen, head of a climate dynamics group at the University of Oxford in the United Kingdom. Allen was not involved in the new study, but his research has focused on carbon’s cumulative impacts on climate.
   Noting that it took less warming, 6°C(10. 8 °F), to lift the world out of the Ice Age, Allen said, "That’s the profundity of the change we’re talking about." The 8-degree rise in global temperatures would blast past the 2°C(3. 8 ° F)limit that nations agreed upon last year in the Paris talks. It also would heat the world to a level approaching that of the early Eocene Period, 52 million to 56 million years ago, when palm trees grew as far north as Alaska? and crocodiles swam in the Arctic.
   Mammals survived Eocene temperatures: this is when early primates appeared. Some horses, however, shrank to the size of house cats, adjusting through evolution to a diet altered either by heat or carbon. Today’s organisms and ecosystems may not be able to adapt to warming over the next 200 to 300 years—an instant on the geological time scale, says Scott Wing, the Smithsonian Institution’s curator of fossil plants. Also, Wing notes that when the Eocene heat began, the Earth’s poles weren’t covered with ice as they are today. "In the future, warming will melt ice caps, which will expose bare ground, increase heat absorption at high latitudes, and cause more warming," Wing says.
   The study predicts that precipitation would quadruple in the tropical Pacific, while it would be reduced by up to third in the Americas and a factor of two over parts of Australia, the Mediterranean, southern Africa, and the Amazon.
   Allen says not only could tropical rain forest systems collapse, but drought in southern Europe and the United States would be " completely catastrophic for agriculture. " Wealthy nations might maintain food supply, but not places like southern Africa. "A lot of people would have to leave, or a lot of people would die," Allen says. [br] Burning all earth’s fossil fuel resources would make its average temperature ______ higher than that before man entered industrial age.
选项 A、2°C
B、6°C
C、8°C
D、17°C
答案 C
解析
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