Trends of atmospheric composition over Eurasia and their response on global climate changes

Based on the analysis of orbital measurements, as well as GEOS-Chem model calculations, a study of trends in the total content of CO, CH4 and NO2 in different periods and seasons of 2003-2022 was made for the Eurasia domain, -20°E - 180°E, 0°N - 80°N. Data from the AIRS and OMI instruments were used as orbital information.

Before calculating the trend distributions, we compared the trend estimates obtained from orbital and ground-based measurements using only synchronous observations, i.e., days when the measurements were carried out by both orbital (AIRS, OMI) and ground-based (IAP RAS and NDACC stations) instruments.

A good agreement has been established between trend distributions obtained from the orbital data and the same distributions obtained from the GEOS-Chem model calculations.

In general, according to average annual estimates, trends over most of Eurasia regions in the period 2003-2022 was negative; however, after 2008 the downward trend slowed down, and in some areas the CO content began to rise.

Thus, a positive trend (change) in CO TC trends after about 2008 was established. In the entire domain under study, this change was about 2–2.5%/year. In the autumn months of 2008-2022 (including November) increase in CO TC was established over almost the entire Eurasia, including Arctic regions and Europe. This growth (at least in Europe) cannot be explained by either anthropogenic emissions or releases from fires. A possible reason for this rising may be the formation of additional CO from methane, the increase in concentrations of which began around the same time (after 2007), and change in the source/sink ratio for CO.

Based on GEOS-Chem calculations with different scenarios for specifying anthropogenic emissions and emissions from fires, the response of CO trends to climate change was calculated. The study was supported by Russian Science Foundation under grant №21-17-00210.