Variability and Long-Term Trends of CO2 & CH4 in European Countries, Using CAMS Global Reanalysis Data

In this study, Copernicus Atmosphere Monitoring Service (CAMS) reanalysis data (EAC4 & EGG4) are used. To capture short-term variations and analyze long-term changes in CO2 and CH4, this study focuses on two specific regions of interest in each of three European countries: Greece, Italy, and France. Both CO2 and CH4 exhibit a positive trend with seasonally averaged increases of over 6% and 2%, respectively, compared to the reference period 2003–2013. Enhanced CH4 concentrations in Greece are observed during winter, primarily linked to anthropogenic sources such as fossil fuel combustion, heating, industrial activities, and gas distribution. Additionally, positive CH4 residuals exceeding 0.6% were detected in autumn, likely due to regional agricultural activities in N. Greece and/or wildfires in Athens. Winter, spring, and autumn are the seasons during which CH4 concentrations are typically highest in the Basilicata and Po Valley regions of Italy, primarily due to agricultural activities, waste management processes, and natural gas extraction, particularly in the Val d’Agri region. Higher CH4 variability was found during winter in France. Regarding CO2, all countries show a large diurnal variability (approximately ± 2 ppm), that of a typical mid-northern-hemisphere site, largely associated with the biospheric cycle of photosynthesis and enhanced by anthropogenic emissions and wildfire episodes.