Response of Atmospheric Composition Trends in 2003–2019 to Climate Changes in Eurasia

The results of GEOS-Chem chemical-transport model (CTM) simulation of methane (CH₄), carbon monoxide (CO), and nitrogen dioxide (NO₂) total column (TC) trends over Eurasia for different periods and seasons during 2003–2019 are presented. Calculations were conducted for different scenarios of anthropogenic and wildfires emissions. The model trend distributions for all of three gases are compared with estimates obtained from satellite AIRS and OMI data. The TC trends for CO, CH₄, and NO₂ are quite well reproduced by the model, both in terms of the overall domain and the specificity of the regional trends, but the trend values are generally overestimated compared to the AIRS v6 satellite data, especially for CO in polluted regions (China and Southeast Asia). A possible reason for such discrepancies could be the uncertainties in the anthropogenic and wildfire inventories used. The response of CO TC trends to global changes has been estimated. One of the possible reasons for the positive dynamics of the CO trend after 2008 could be a global increase in methane concentrations, which started around 2007, and additional CO production from methane oxidation.