Climate Change,the Measure of Global Warming, May 11st, 2013, Economist
气候变化，对全球变暖的测量，经济学人，2013年5月11日
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).
5月4日中午，夏威夷莫纳罗亚观测站测量到在其附近大气层中，二氧化碳的浓度达到了400ppm。
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.
这天的平均浓度为399.73ppm。观测站研究人员预计，在接下来的几天，该数值将会超过400ppm。
The last time such values prevailed on Earth was in the Pliocene epoch，4m years ago, when jungles covered northern Canada.
距离上一次地球上出现这样的浓度，是在4百万年以前的上新世时期，那时候，加拿大北部地区被大片丛林所覆盖。
Mauna Loa is the benchmark for CO2 measurement (and has been since 1958, see chart) because Hawaii is so far from large concentrations of humanity.
莫纳罗亚地区是二氧化碳测量基准（从1958年以来就是如此，如图所示）。这是因为夏威夷远离人类大规模的聚齐地。
The Arctic,by contrast,gets a lot of polluted air from Europe and North America.
相比之下，北极有大量来自欧洲与北美洲的污染空气。
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.
据在莫纳罗亚负责监控的Pieter Tans称，今年5月的平均浓度可能也会达到400ppm，而在2014年或2015年的春季，数值将会达到400ppm。
Mauna Loa's readings are one of the world's longest-running measurement series.
莫纳罗亚测量的测量值是世界上使用时间最长的测量标准之一。
The first，made in March 1958，was 315ppm. That means they have risen by a quarter in 55 years.
第一次的测量值是在1958年3月，为315ppm。这意味着，在55年内，二氧化碳浓度增加了四分之一。
In the early 1960s they were going up by 0.7ppm a year.
在20世纪60年代早期，二氧化碳浓度以每年0.7ppm的速度增长。
The rate of increase is now 2.1 ppm—three times as fast—reflecting the relentless rise in greenhouse-gas emissions.
现在的增长速度为2.1ppm，相当于那时的三倍，这说明温室气体的排放一直都有增无减。
As a rule of thumb，CO2 concentrations will have to be restricted to about 450ppm if global warming is to be kept below 20℃(a level that might possibly be safe).
一般来说，如果全球温度上升保持在20摄氏度以下（可能安全的标准），二氧化碳的浓度必须限制在450ppm左右。
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.
因为二氧化碳可以在大气层中存在几十年，所以要想达到450ppm，必须立刻减少对这种气体的人工排放，然后在2075年达到零排放。
There seems no chance of that. Emissions are still going up. At current rates，the Mauna Loa reading will rise above 450ppm in 2037.Thank you.
照目前形势看，这似乎是不可能的。废气依然有增无减。以目前的速度，2037年莫纳罗亚测量的二氧化碳浓度将会超过450ppm。谢谢。
