Significant climate impacts of aerosol changes driven by growth in energy use and advances in emissions control technology

Abstract. Anthropogenic aerosols have increased significantly since the industrial revolution, driven largely by growth in emissions from energy use in sectors including power generation, industry, and transport. Advances in emission control technologies since around 1970, however, have partially counteracted emissions increases from the above sectors. Using the fully-coupled Community Earth System Model, we quantify the effective radiative forcing (ERF) and climate response to 1970–2010 aerosol emission changes associated with the above two policy-relevant emission drivers. Emissions from energy use growth generate a global mean aerosol ERF of −0.31 W m −2 , and result in a global mean cooling of −0.35 K and a precipitation reduction of −0.03 mm day −1 . By contrast, the avoided emissions from advances in emission control technology, which benefit air quality, generate a global mean ERF of +0.21 W m −2 , a global warming of +0.10 K and global mean precipitation increase of +0.01 mm day −1 . The total net aerosol impacts on climate are dominated by energy use growth, from Asia in particular. However, technology advances outweigh energy use growth over Europe and North America. Also, the Arctic climate is significantly affected by aerosol emission changes from Europe, North America, and Asia. Various non-linear processes are involved along the pathway from aerosol emissions to radiative forcing and ultimately to climate responses, suggesting that the diagnosed aerosol forcing and effects must be interpreted in the context of experiment designs. Further, the temperature response per unit aerosol ERF varies significantly across many factors, including location and magnitude of emission changes, implying that ERF, and the related metrics, need to be used very carefully for aerosols. Future aerosol emission pathways have large temporal and spatial uncertainties; our findings provide useful information for both assessing and interpreting such uncertainties, and may help inform future climate change impact reduction strategies.