Atmospheric CO 2 gradients are usually dominated by the signal from net terrestrial biological fluxes, despite the fact that fossil fuel combustion fluxes are larger in the annual mean. Here, we use a six year long series of 14 CO 2 and CO 2 measurements obtained from vertical profiles at two northeast U.S. aircraft sampling sites to partition lower troposphere CO 2 enhancements (and depletions) into terrestrial biological and fossil fuel components (C bio and C ff ). Mean C ff is 1.5 ppm, and 2.4 ppm when we consider only planetary boundary layer samples. However, we find that the contribution of C bio to CO 2 enhancements is large throughout the year, and averages 60% in winter. Paired observations of C ff and the lower troposphere enhancements (Δ gas ) of 22 other anthropogenic gases (CH 4 , CO, halo‐ and hydrocarbons and others) measured in the same samples are used to determine apparent emission ratios for each gas. We then scale these ratios by the well known U.S. fossil fuel CO 2 emissions to provide observationally based estimates of national emissions for each gas and compare these to “bottom up” estimates from inventories. Correlations of Δ gas with C ff for almost all gases are statistically significant with median r 2 for winter, summer and the entire year of 0.59, 0.45, and 0.42, respectively. Many gases exhibit statistically significant winter:summer differences in ratios that indicate seasonality of emissions or chemical destruction. The variability of ratios in a given season is not readily attributable to meteorological or geographic variables and instead most likely reflects real, short‐term spatiotemporal variability of emissions.
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Miller et al. (2012) studied this question.