Attribution of aerosol direct radiative forcing in China and India to emitting sectors

Abstract

Strict emission control measures are being implemented in China and India to improve air quality and protect human health, yet current air quality driven and sector based measures without consideration of climate effects would likely taccelerate warming. In this study, we attribute aerosol direct radiative forcing in China and India to emitting sectors using a fully online coupled meteorology-chemistry model (WRF-Chem, Weather Research and Forecasting Model coupled with Chemistry) for the entire year of 2013. Our simulations show that the observed spatial and temporal variations of aerosol concentrations and optical properties are generally reproduced by the model, although sulfate is biased low in winter due to missing aqueous/heterogeneous pathways in the model. Aerosols from all sectors result in negative direct forcing at the top of the atmosphere (TOA) in both China (−2.21 W/m2) and India (−3.18 W/m2), which are largely contributed by the power sector. The residential sector in both China and India largely heats the atmosphere because of its dominant contribution to black carbon emissions. In both China and India, the longwave radiative forcing (0.86 and 1.21 W/m2 for China and India) is tiny compared to the shortwave radiative forcing (−3.07 and −4.39 W/m2 for China and India). The seasonality of sectoral radiative forcing in China is different from that in India. These results suggest that residential sector should be targeted to achieve both air quality and climate change goals, yet the control of emissions from the power sector is very likely to accelerate warming.