Testing the hypothesis of the presence of a trend in the airborne fraction (AF), defined as the fraction of CO2 emissions remaining in the atmosphere, has attracted much attention, with the overall consensus that no statistical evidence is found for a trend in the data (Knorr, 2009; Gloor et al., 2010; Raupach et al., 2014; Bennedsen et al., 2019). In a paper recently published in this journal, van Marle et al. (van Marle et al., 2022) introduce a new data set for land use and land cover change CO2 emissions (LULCC), and from a Monte Carlo simulation analysis of these data, the authors conclude that there is a negative trend in the AF. We argue that the Monte Carlo design of van Marle et al. is not conducive to determine whether there is a trend in the AF and therefore presents no compelling statistical evidence. A re-examination of the data using a variety of statistical tests finds no evidence of a trend on the whole sample and some evidence of a positive trend when a break in the level of the AF is accounted for.

翻译：检验大气留存比（即排放至大气中CO₂的留存比例）是否存在趋势的假设一直备受关注，目前学界普遍认为现有数据未发现统计意义上的趋势证据（Knorr, 2009; Gloor等, 2010; Raupach等, 2014; Bennedsen等, 2019）。van Marle等学者近期在本刊发表的论文中（van Marle等, 2022），引入了一套土地利用与土地覆盖变化CO₂排放（LULCC）的新数据集，并通过对该数据集的蒙特卡洛模拟分析，得出大气留存比呈下降趋势的结论。我们认为van Marle等采用的蒙特卡洛设计方案不足以判定大气留存比是否真实存在趋势，因此未能提供具有说服力的统计证据。通过运用多种统计检验方法对数据进行重新分析，结果显示全样本期间未发现显著趋势，但在考虑大气留存比水平突变的条件下，发现了部分支持上升趋势的证据。