Separation of biospheric and fossil fuel fluxes of CO2 by atmospheric inversion of CO2 and 14CO2 measurements: Observation System Simulations
Separation of biospheric and fossil fuel fluxes of CO2 by atmospheric inversion of CO2 and 14CO2 measurements: Observation System Simulations
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DOI：
10.5194/acp-16-5665-2016
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发表时间：
2016-01-01
影响因子：
6.3
通讯作者：
Lehman, Scott
中科院分区：
文献类型：
--
作者：
Basu, Sourish;Miller, John Bharat;Lehman, Scott
已知大多数发达国家燃烧化石燃料产生的国家年度CO2总排放量可能在5-10aEuro-%之内。然而，区域和月尺度的排放量估计或发展中国家的不确定性不可避免地更大（数量未知）。鉴于最近国际社会努力制定减排目标，独立确定和核实区域和国家规模的化石燃料二氧化碳排放量可能变得越来越重要。在这里，我们利用这一事实，即精确测量的C-14在CO2中提供了一个很大程度上公正的示踪最近添加的化石燃料产生的CO2在大气中，并提出了一个大气反演技术，共同同化观测CO2和（CO2）-C-14，以同时估计化石燃料排放和生物圈交换通量的CO2。在一组观测系统模拟实验（OSSEs）中使用这种方法，我们表明，鉴于2010年（CO2）-C-14测量的覆盖范围（北美969，全球1063），我们可以恢复美国全国化石燃料总排放量超过1aEuro-%，大多数月份在5aEuro-%以内。增加（CO2）-C-14观测的数量，使其在北美地区每年接近5000次，正如美国国家科学院（NAS）最近建议的那样（Pacala等人，2010年），我们将美国所有月份的月排放量恢复到5aEuro-%以内，也将指定数据覆盖相对密集的较小的高排放区域恢复到5aEuro- %以内，例如新英格兰州或NY-NJ-PA三州地区。这一结果表明，鉴于最先进的运输模型的不断改进，与NAS建议的规模类似的测量计划可以在区域和国家范围内对自下而上的化石燃料CO2库存进行独立验证。此外，我们表明，双示踪剂反演框架可以检测和最大限度地减少偏差估计的生物圈通量，否则会出现在一个传统的CO2只反演时，规定固定的，但不准确的化石燃料通量。
National annual total CO2 emissions from combustion of fossil fuels are likely known to within 5-10aEuro-% for most developed countries. However, uncertainties are inevitably larger (by unknown amounts) for emission estimates at regional and monthly scales, or for developing countries. Given recent international efforts to establish emission reduction targets, independent determination and verification of regional and national scale fossil fuel CO2 emissions are likely to become increasingly important. Here, we take advantage of the fact that precise measurements of C-14 in CO2 provide a largely unbiased tracer for recently added fossil-fuel-derived CO2 in the atmosphere and present an atmospheric inversion technique to jointly assimilate observations of CO2 and (CO2)-C-14 in order to simultaneously estimate fossil fuel emissions and biospheric exchange fluxes of CO2. Using this method in a set of Observation System Simulation Experiments (OSSEs), we show that given the coverage of (CO2)-C-14 measurements available in 2010 (969 over North America, 1063 globally), we can recover the US national total fossil fuel emission to better than 1aEuro-% for the year and to within 5aEuro-% for most months. Increasing the number of (CO2)-C-14 observations to similar to 5000 per year over North America, as recently recommended by the National Academy of Science (NAS) (Pacala et al., 2010), we recover monthly emissions to within 5aEuro-% for all months for the US as a whole and also for smaller, highly emissive regions over which the specified data coverage is relatively dense, such as for the New England states or the NY-NJ-PA tri-state area. This result suggests that, given continued improvement in state-of-the art transport models, a measurement program similar in scale to that recommended by the NAS can provide for independent verification of bottom-up inventories of fossil fuel CO2 at the regional and national scale. In addition, we show that the dual tracer inversion framework can detect and minimize biases in estimates of the biospheric flux that would otherwise arise in a traditional CO2-only inversion when prescribing fixed but inaccurate fossil fuel fluxes.