Ritesh Gautam, Piyushkumar Patel, Manoj Singh, Tianjia Liu , Loretta Mickley, Hiren Jethva, Ruth DeFries

Air pollution in India severely impacts the air quality, public health and economy in one of the world’s most densely populated regions. Persistent agricultural fires during the late-autumn period and widespread winter-time pollution contribute to the extreme smog in south Asia, especially affecting the entire northern India. While the links between anthropogenic emissions, air quality and health impacts have been well recognized, the association of smog and its intensification with climatic trends in the lower troposphere, where aerosol pollution and its radiative effects manifest, are not understood well. Here we use long-term satellite data to show a significant increase in aerosol exceedances over northern India, resulting in sustained aerosol-induced atmospheric warming and surface cooling trends over the last two decades. We further find several lines of evidence that these aerosol radiative effects may have amplified a multidecadal (1980-2019) strengthening of lower tropospheric stability along with an increase in relative humidity, in turn intensifying the smog and leading to more than fivefold increase in poor visibility days. Given this crucial aerosol-radiation-meteorological feedback, we anticipate results from this study will help inform mitigation strategies supporting stronger region-wide measures, which are critical for solving the smog challenge in India.