The world’s leading climate scientists have set out in detail for the first time how much more carbon dioxide humans can pour in

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问题     The world’s leading climate scientists have set out in detail for the first time how much more carbon dioxide humans can pour into the atmosphere without triggering dangerous levels of climate change—and concluded that more than half of mat global allowance has been used up.
    If people continue to emit greenhouse gases at current rates, the accumulation of carbon in the atmosphere could mean that within as little as two to three decades the world will face nearly inevitable warming of more than 2℃, resulting in rising sea levels, heatwaves, droughts and more extreme weather.
    This calculation of the world’s "carbon budget" was one of the most striking findings of the Intergovernmental Panel on Climate Change(IPCC), the expert panel of global scientists who on Friday produced the most comprehensive assessment yet of our knowledge of climate change at the end of their four-day meeting in Stockholm.
    The 2,000-plus page report, written by 209 lead authors, also found it was "unequivocal" that global warming was happening as a result of human actions, and that without "substantial and sustained" reductions in greenhouse gas emissions we will breach the symbolic threshold of2℃ of warming, which governments around the world have pledged not to do.
    John Kerry, the US secretary of state, said in a statement: "This is yet another wakeup call: those who deny me science or choose excuses over action are playing with fire. "
    " Once again, the science grows clearer, the case grows more compelling, and the costs of inaction grow beyond anything that anyone with conscience or commonsense should be willing to even contemplate," he added.
    The IPCC also rebuffed me argument made by climate sceptics that a "pause" for the last 10 -15 years in the upward climb of global temperatures was evidence of flaws in their computer models. In the summary for policymakers, published on Friday morning after days of deliberations in the Swedish capital, me scientists said: " Each of the last three decades has been successively warmer at me Earth’s surface man any preceding decade since 1850. In the northern hemisphere, 1983 -2012 was likely the warmest 30-year period of the last 1,400 years. "
    Thomas Stocker, co-chair of the report working group, said measuring recent years in comparison to 1998, an exceptionally hot year, was misleading and that temperature trends could only be observed over longer periods, of about 30 years.
    Natural variability was cited as one of the reasons for warming being less pronounced in the last 15 years, and the role of the oceans in absorbing heat, which is still poorly understood.
    "There are not sufficient observations of the uptake of heat, particularly into the deep ocean, that will be one of the possible mechanisms that would explain this warming hiatus(间断)," said Stocker.
The "threshold of2℃ of warming" in Paragraph Four implies that______.

选项 A、it is the maximum amount of gas emissions in the atmosphere
B、it is the entrance of carbon dioxide emissions into the atmosphere
C、it is a starting point the world governments determined to reach
D、it is a critical point the world governments determined not to break

答案D

解析 推断题。根据第四段最后一句中的which governments around the world have pledged not to do可知,2℃为各国政府发誓不去突破的临界点,[D]符合文意。
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