单选题 At noon on May 4th the carbon-dioxide concentration in the atmosphere around the Mauna Loa Observatory in Hawaii hit 400 parts per million (ppm). The average for the day was 399.73 and researchers at the observatory expect this figure, too, to exceed 400 in the next few days. The last time such values prevailed on Earth was in the Pliocene epoch (上新世) 4m years ago, when jungles covered northern Canada.
There have already been a few readings above 400ppm elsewhere—those taken over the Arctic Ocean in May 2012, for example—but they were exceptional. Mauna Loa is the benchmark (标准) for CO2 measurement because Hawaii is so far from large concentrations of humanity. The Arctic, by contrast, gets a lot of polluted air from Europe and North America.
The concentration of CO2 peaks in May, falls until October as plant growth in the northern hemisphere's summer absorbs the gas, and then goes up again during winter and spring. This year the average reading for the whole month will probably also reach 400ppm, according to Pieter Tans, who is in charge of monitoring at Mauna Loa, and the seasonally adjusted annual figure will reach 400ppm in the spring of 2014 or 2015.
Mauna Loa's readings are one of the world's longest-running measurement series. The first, made in March 1958, was 315ppm. That means they have risen by a quarter in 55 years. In the early 1960s they were going up by 0.7ppm a year. The rate of increase is now 2.1ppm—three times as fast—reflecting the relentless rise in green-house-gas emissions.
As a rule of thumb, CO2 concentrations will have to be restricted to about 450ppm if global warming is to be kept below 2 degree. Because CO2 stays in the atmosphere for decades, artificial emissions of the gas would have to be cut immediately, and then fall to zero by 2075, in order to achieve 450ppm. There seems no chance of that. Emissions are still going up. At current rates, the Mauna Loa reading will rise above 450ppm in 2037.
单选题 We can learn from the first paragraph that ______.
  • A.Mauna Loa Observatory is located in northern Canada
  • B.about 4 million years ago, jungles covered northern part of the Earth
  • C.the carbon-dioxide concentration is expected to exceed 400ppm in the next few days
  • D.it is the first time in human history that carbon-dioxide concentration reaches 400ppm
【正确答案】 C
【答案解析】[解析] 推理题。 选项与原文对比。A根据Mauna Loa定位到首句the Mauna Loa Observatory in Hawaii，说明Mauna Loa是在夏威夷而不是加拿大。B定位到尾句：4m years ago, when jungles covered northern Canada，故B选项错误。C原文：researchers at the observatory expect this figure, too, to exceed 400 in the next few days，而this figure指代的就是carbon-dioxide concentration，故正确。D原文：The last time such values prevailed on Earth was in the Pliocene epoch(上新世)4m years ago，说明达到400ppm这个数据不是历史第一次。
单选题 Mauna Loa is the standard for CO2 measurement for the reason that ______.
  • A.Hawaii has small concentrations of human
  • B.its air has been polluted by Europe and North America
  • C.Hawaii has far larger concentrations of humanity than other places
  • D.the Arctic gets a lot of polluted air from Europe and North America
【正确答案】 A
【答案解析】[解析] 细节题。
选项与原文对比。根据CO2 measurement定位到第二段第三行：Mauna Loa is the benchmark (标准) for CO2 measurement because Hawaii is so far from large concentrations of humanity，题干问的是原因，for the reason that=because，故答案在because之后，即Hawaii is so far from large concentrations of humanity=A．Hawaii has small concentration of human，其中far from large=small.
单选题 The third paragraph tells us that ______.
  • A.the concentration of CO2 rises during summer
  • B.the concentration of CO2 goes down during winter
  • C.the figure in the spring of 2015 will not reach 400ppm
  • D.Pieter Tans is the man in charge of supervision at Mauna Loa
【正确答案】 D
【答案解析】[解析] 推理题。
选项与原文对比。首先A、B两项是正话反说，其实表达的是同一个意思，可以排除。原文：The concentration of CO2 peaks in May, falls until October as plant growth in the northern hemisphere's summer absorbs the gas, and then goes up again during winter and spring，说明CO2浓度是五月到十月下降，即夏天下降，而冬天到春天期间上涨，A、B两项和原文意思完全相反。C原文：figure will reach 400ppm in the spring of 2014 or 2015.故C错误。D原文：Pieter Tans, who is in charge of monitoring at Mauna Loa，其中monitoring=D项supervision。
单选题 The rise of green-house-gas emissions leads to ______.
  • A.the decrease ofppm statistics
  • B.the faster increasing rate of ppm
  • C.the slower increasing rate of ppm
  • D.the highest readings in recorded history
【正确答案】 B
【答案解析】[解析] 细节题。 选项与原文对比。原文第四段最后一句：The rate of increase is now 2.1ppm—three times as fast—reflecting the relentless rise in green-house-gas emissions.增长率如今是2.1ppm——是之前的三倍——反映了温室气体排放量不断增长。也就是说温室气体排放导致了ppm增长率变快，即选项B是正确的。
单选题 Which is true according to the last paragraph?
  • A.CO2 remains in the atmosphere for several dozen years.
  • B.At current rates, Mauna Loa reading will rise above 450ppm by 2075.
  • C.The chance of cutting emissions and achieving 450ppm by 2075 is good.
  • D.Human's gas emissions have been cut at once in order to achieve 450ppm.
【正确答案】 A
【答案解析】[解析] 细节题。
选项与原文对比。A原文：Because CO2 stays in the atmosphere for decades...其中stays=remains；decades=several dozen years，故A正确。B项At current rates, the Mauna Loa reading will rise above 450ppm in 2037，原文提到的是2037年，B是2075年，故错误。C原文：...artificial emissions of the gas would have to be cut immediately, and then fall to zero by 2075, in order to achieve 450ppm. There seems no chance of that...原文说的是no chance，该选项说的是chance is good，故错误。D原文：...artificial emissions of the gas would have to be cut immediately，and then fall to zero by 2075, in order to achieve 450ppm，原文说的是have to be cut，而不是have been cut，故D选项错误。答案为A。