Atmospheric trends and radiative forcings of CF4 and C2F6 inferred from firn air.
Atmospheric trends and radiative forcings of CF4 and C2F6 inferred from firn air.
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DOI：
10.1021/es061710t
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发表时间：
2007-02
影响因子：
11.4
通讯作者：
D. Worton;W. Sturges;L. K. Gohar;K. Shine;P. Martinerie;D. Oram;S. Humphrey;Paul Begley;L. Gunn;J. Barnola;J. Schwander;R. Mulvaney
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文献类型：
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作者：
D. Worton;W. Sturges;L. K. Gohar;K. Shine;P. Martinerie;D. Oram;S. Humphrey;Paul Begley;L. Gunn;J. Barnola;J. Schwander;R. Mulvaney
两个强大的温室气体，四氟甲烷（CF 4）和六氟乙烷（C2 F6）的大气历史，已经重建了20世纪的基础上，从两个半球的积雪空气测量。重建的大气趋势表明，CF 4和C2 F6的混合比在20世纪世纪分别增加了约2倍和约10倍。最初，混合比的增加与原铝产量的增加相吻合。然而，在1990年代，四氟化碳在大气中的增长速度明显减慢，这支持了最近铝工业报告中四氟化碳排放量减少的说法。这项工作说明了CF 4和C2 F6之间不断变化的关系，这可能主要是由于铝工业的排放量减少和半导体工业C2 F6排放量的快速增长。在较老的积雪空气中对C2 F6的测量表明，天然背景混合比<0.3万亿分之一（ppt），表明这种气体的天然来源可以忽略不计。然而，推断出CF 4具有34 - 1 ppt的工业化前混合比（当代水平的约50%）。这与Harnisch等人（18）以前的工作非常一致，并为他们的结果提供了独立的证实。由于CF 4和C2 F6具有较大的全球变暖潜势，这些结果对辐射强迫计算具有重要意义。与工业化前的浓度相比，CF 4和C2 F6的辐射强迫在过去50年中有所增加，2001年的数值分别为4.1 x 10（-3）Wm（-2）和7.5 x 10（-4）Wm（-2）。由于主要的温室气体，这些强迫与目前的强迫相比很小，但是，如果目前的趋势继续下去，它们将继续增加，因为这两种气体基本上都有无限的寿命。因此，减少全氟化碳排放的动力很大，通过执行《京都议定书》，大气增长率今后可能会下降。
The atmospheric histories of two potent greenhouse gases, tetrafluoromethane (CF4) and hexafluoroethane (C2F6), have been reconstructed for the 20th century based on firn air measurements from both hemispheres. The reconstructed atmospheric trends show that the mixing ratios of both CF4 and C2F6 have increased during the 20th century by factors of approximately 2 and approximately 10, respectively. Initially, the increasing mixing ratios coincided with the rise in primary aluminum production. However, a slower atmospheric growth rate for CF4 appears to be evident during the 1990s, which supports recent aluminum industry reports of reduced CF4 emissions. This work illustrates the changing relationship between CF4 and C2F6 that is likely to be largely the result of both reduced emissions from the aluminum industry and faster growing emissions of C2F6 from the semiconductor industry. Measurements of C2F6 in the older firn air indicate a natural background mixing ratio of <0.3 parts per trillion (ppt), demonstrating that natural sources of this gas are negligible. However, CF4 was deduced to have a preindustrial mixing ratio of 34 -1 ppt (-50% of contemporary levels). This is in good agreement with the previous work of Harnisch et al. (18) and provides independent confirmation of their results. As a result of the large global warming potentials of CF4 and C2F6, these results have important implications for radiative forcing calculations. The radiative forcings of CF4 and C2F6 are shown to have increased over the past 50 years to values in 2001 of 4.1 x 10(-3) Wm(-2) and 7.5 x 10(-4) Wm(-2), respectively, relative to preindustrial concentrations. These forcings are small compared to present day forcings due to the major greenhouse gases but, if the current trends continue, they will continue to increase since both gases have essentially infinite lifetimes. There is, therefore, a large incentive to reduce perfluorocarbon emissions such that through the implementation of the Kyoto Protocol, the atmospheric growth rates may decline in the future.