Urban Air Pollution as a Driver of Climate Forcing in Central and South Asia: Causal Evidence from Tashkent (Uzbekistan) and Lahore (Pakistan)

<title>Abstract</title> <p>Urban air pollution is increasingly recognized not only as a public health crisis but also as an important contributor to regional climate forcing. However, empirical evidence demonstrating the causal relationship between urban pollution and localized climate change remains limited, particularly in rapidly urbanizing regions of Central and South Asia. This study investigates the causal impact of urban air pollution on climate forcing using comparative case studies from Tashkent in Uzbekistan and Lahore in Pakistan two metropolitan areas that have experienced severe deterioration in air quality over the past decade. The analysis integrates satellite-derived aerosol optical depth (AOD), ground-level particulate matter (PM₂.₅ and PM₁₀), and meteorological datasets spanning 2005–2023. A causal inference framework combining Granger causality testing, panel regression models, and radiative forcing estimation was applied to quantify the contribution of urban pollution to localized climate anomalies. Results indicate that annual average PM₂.₅ concentrations reached 58–72 µg m⁻³ in Tashkent and 92–110 µg m⁻³ in Lahore, exceeding the World Health Organization air quality guideline of 5 µg m⁻³ by factors of 12 and 20, respectively. The statistical analysis confirms a significant causal relationship (p &lt; 0.01) between particulate pollution levels and regional temperature anomalies. Radiative forcing estimates suggest that aerosol–climate interactions associated with urban pollution contributed + 0.18 to + 0.32 W m⁻² of net regional radiative forcing in Tashkent and + 0.25 to + 0.41 W m⁻² in Lahore during peak pollution periods. Over the study period, urban pollution was associated with 0.21°C of annual mean temperature increase in Tashkent and 0.31°C in Lahore, accounting for approximately 18–23% of observed urban warming trends. Seasonal analysis further reveals that wintertime aerosol accumulation amplifies atmospheric heating and boundary-layer stability, intensifying both smog formation and localized climate feedbacks. These findings demonstrate that urban air pollution can act as a measurable driver of regional climate forcing in rapidly growing cities. The results highlight the importance of integrating air quality management with climate mitigation strategies in Central and South Asia, where urban emissions increasingly influence both public health outcomes and regional climate dynamics.</p>