Climate-driven air pollution extremes over Portugal (2012–2025): insights from CAMS data

Air pollution poses significant risks to human health and ecosystems, being strongly influenced by meteorological conditions and climate-driven extremes variability. In southern Europe, climate change is expected to intensify heatwaves, droughts, and wildfire activity, thereby increasing the likelihood of compound events and exacerbating the severity of air pollution episodes. This study analyses the spatiotemporal variability of atmospheric pollutants over the mainland Iberian Peninsula for the period 2012–2025, using data provided by Copernicus Atmosphere Monitoring Service (CAMS). The use of CAMS data enables a spatially consistent assessment of air quality across regions that are less covered by national monitoring networks. The applied analysis focuses on key pollutants, namely carbon monoxide CO, PM₁₀, and PM₂.₅, examining their intra-annual and inter-annual variability, inter-pollutant relationships, and associations with meteorological conditions conducive to extreme events. 

The methodology used includes statistical and spatial analysis to identify the spatiotemporal patterns of key pollutants (CO, PM10, PM2.5) from CAMS reanalysis data and in situ measurements for the study period from 2012 to 2025. The influence of atmospheric conditions on the dispersion and concentration of pollutants was also addressed, with particular attention to atmospheric circulation patterns that can influence the occurrence of forest fires and consequent episodes of pollutant concentration exceedances. Results show marked seasonal cycles and substantial inter-annual variability in pollutant concentrations, with extreme pollution episodes frequently co-occurring with heatwaves, droughts, and periods of intense wildfire activity. Confirming that these compound events are characterised by simultaneous meteorological drivers and elevated pollutant concentrations, leading to repeated exceedances of air quality thresholds. CAMS data successfully captures the spatial and temporal signatures of these extremes, particularly for CO and particulate matter, highlighting regions recurrently affected by compound fire–air pollution events. By linking air pollution extremes to climate-related extremes, this work advances understanding of compound climate–air quality events and provides a basis for future attribution studies assessing the role of climate change in modulating air pollution extremes in the Iberian Peninsula.