是否有一些复杂的因素?
我一直在做一些思考和研究关于这个和一些可能相关的问题是:
计算停留时间的变化可由各种原因引起;测量位置、使用的观测次数和观测记录的长度。
测量位置可能是最重要的变化来源,因为根据测量位置的不同,结果可能会有很大差异。需要多个观测地点测量所谓的背景气团,才能很好地表明二氧化碳在大气中的全球平均停留时间。我想说你对复杂因素的理解是正确的。当地的影响很重要,因为CO_2$的排放因其来源不同而具有不同的放射性碳特征。燃烧化石燃料产生的二氧化碳不含放射性碳,而核工业排放少量的纯二氧化碳(虽然不一定是以二氧化碳的形式)。 The natural sources and sinks of $CO_2$ (biosphere and ocean) are also not in equilibrium with the atmosphere since the atomic bomb tests in 1950s and 1960s. Immediately after the bomb tests, the large amount of $^{14}C$ produced in the atmosphere meant that it was enhanced in $^{14}CO_2$ compared to the biosphere and the ocean. Since then, $^{14}CO_2$ has decreased in the atmosphere, as it was taken up by the biosphere ant the oceans. This lead to an such a large increase in $^{14}C$ in the biosphere and the surface ocean, that they are now enhanced compared to the atmosphere.
This graph including the oceans should explain what I mean.