Climate drivers of airborne pollen variability: 31 years of monitoring in Barcelona (NE Iberian Peninsula)

Climate change is increasingly modifying airborne pollen dynamics, with key implications for aeroallergen exposure in Mediterranean urban environments. This study analyses 31 years (1994–2024) of aerobiological and meteorological data from Barcelona (NE Iberian Peninsula) to assess long-term trends in pollen concentration, phenology, and their relationships with local climate variables and large-scale atmospheric circulation patterns. Meteorological records show significant warming, including higher autumn and summer maximum temperatures and summer minimum temperatures, together with reduced December precipitation and spring wind speed. Among the studied teleconnection indices, the Atlantic Multidecadal Oscillation (AMO) is the only index showing a significant positive trend at annual and winter scales, consistent with the predominance of a warm AMO phase during most of the 1994–2024 study period. Pollen trends indicate that arboreal taxa are more responsive to climatic variability than shrubs or herbaceous plants. Several tree taxa, notably Alnus and Quercus , exhibit increasing Annual Pollen Integrals and maximum daily concentrations, whereas shrubs show no significant trends. Pollen detection advances in most taxa, while duration shortens in deciduous Quercus and lengthens in Urticaceae. Total pollen shows significant increases in both annual integrals and daily peak concentrations. Air temperature, precipitation, and wind speed exert taxon-specific effects on pollen seasonality, with warmer conditions advancing the pollen season in 65% of taxa, and reduced spring wind speeds potentially limiting pollen dispersion. Teleconnection patterns, particularly the AMO, significantly modulate pollen timing and magnitude. Overall, these results highlight the strong sensitivity of airborne pollen dynamics to ongoing warming and atmospheric circulation variability, underscoring the importance of long-term aerobiological monitoring for public-health planning in Mediterranean cities.