A Review of the Effect of the Chemical Composition of the Atmosphere on the Dry Gas Constant over Multiple Time Scales

Abstract The calculation of the dry-air constant depends on the concentrations of the main atmospheric constituents. The variation in N2, O2 and CO2 concentration over the last 23 million years has a small, but calculable, effect on the value of the constant. For modern times, a comparison is made between some estimates in the literature, and a heuristic adjustment of the concentrations of the main components is proposed, in order to account for the CO2 increase during the last decades; a confidence interval for the value of the constant is also estimated. Over longer time scales two periods are analyzed: the Christian era (Period I), and the last 23 Ma (Period II). It is found that the increase in CO2 that started with the Industrial Revolution has an impact on the constant over Period I, but that changes in the constant during Period II are caused by increasing O2 levels.

摘要 干空气常数的计算取决于大气主要组分的浓度。过去2300万年中氮气（N₂）、氧气（O₂）与二氧化碳（CO₂）的浓度变化，会对该常数的数值产生微小但可计算的影响。针对现代时期，本文对现有文献中的若干估算结果开展对比，并提出针对大气主要组分浓度的启发式调整方案，以契合近数十年来二氧化碳浓度的上升趋势；同时还估算了该常数值的置信区间。在更长的时间尺度上，本文分析了两个时段：公元纪年时期（时段I）与过去23百万年（23 Ma）。研究发现，工业革命以来出现的二氧化碳浓度升高对时段I内的干空气常数存在影响，而时段II内该常数的变化则由氧气浓度的升高所主导。