Climate-Driven Changes in Air Quality: Trends Across Emission and Socioeconomic Pathways

Climate change (CC) and air pollution are closely interlinked environmental challenges that significantly affect human health and quality of life, especially in urban and industrialized regions. This study conducted a comprehensive investigation on how future climate scenarios may affect air quality and related human impacts, using a Southern European country (Portugal) for illustration. The study employed the most up-to-date future climate projections (Shared Socioeconomic Pathways—SSP) that were dynamically downscaled for Portugal. High-resolution simulations were carried out using the Weather Research & Forecasting (WRF) model, providing data for relevant meteorological variables that most affect air quality, for three future climate scenarios: fossil-fueled development (SSP5-8.5), regional inequality (SSP3-7.0), and a middle-of-the-road future (SSP2-4.5). Current and future air quality was simulated with the CHIMERE chemical transport model driven by WRF downscaled data and future emissions from the SSP v2.0 database. Results show that CC will impact nitrogen oxides (NO 2 ), ozone (O 3 ), and particulate matter (PM) concentrations over Portugal, with only agricultural emissions increasing in all scenarios. PM and NO 2 will decrease in urban areas, over the short and long term, mainly for more conservative scenarios (SSP2-4.5 and SSP3-7.0), while O 3 will increase over mainland Portugal (except for coastal/urban areas). Regarding human health, premature deaths are expected to be highest in urban areas, with reductions projected for NO 2 and PM 2.5 under SSP2-4.5 and increases in O 3 -related mortality under SSP5-8.5. Overall, SSP2-4.5 presents the most sustainable outcomes, highlighting the importance of integrating air quality management and health impact assessments into climate adaptation strategies to promote long-term environmental sustainability in southern Europe, consistent with the United Nations Sustainable Development Goals (SDGs).