The continuous record of carbon dioxide and methane at the atmospheric station at Plateau Rosa: analysis of global trends and identification of source regions in Europe

High mountain sites offer strategic spots for long-term monitoring of greenhouse gases, thanks to their altitude and distance from local anthropogenic emissions that enable measurements of well-mixed troposphere. At the atmospheric monitoring station at Plateau Rosa carbon dioxide (CO₂) and methane (CH₄) mole fractions are measured continuously with a cavity ring-down spectrometer. The station is situated in in the north-western Italian Alps near Mt. Cervino at 3480 meters AMSL and is part of the ICOS (Integrated Carbon Observation System) framework and WMO/GAW program (World Meteorological Organisation/Global Atmospheric Watch, Identification Code: PRS).

In this study we show the CO₂ and CH₄ record measured at the station since 2018 in comparison with NOAA's global trends, demonstrating the PRS representativeness of global mole fractions, and we select pollution events at regional scale that led to significant CO₂ and CH₄ mole fraction enhancements at the station. Analysis of these events using the FLEXPART-COSMO modelling framework for tracing back air masses draws attention to specific hotspot areas in Europe. We identified five pollution events during the 2021-2024 period, lasting more than six hours, associated with air masses coming mainly from the Po Valley, in Italy, and European countries such as France, Germany, Belgium, the Netherlands and the UK.

We finally demonstrate how observations of CO₂ and CH₄ at Plateau Rosa provide a continuous and accurate record of the two major greenhouse gases, which can be used, together with atmospheric transport modelling, to address specific source regions in Europe for targeted reduction efforts.