Integrated assessment of air quality and climate change for policy-making: highlights of IPCC AR5 and research challenges

Recently, air quality in China has received significant attention, especially since the unprecedented heavily polluted haze episodes were observed in populated areas of central and eastern China [1]. Major atmospheric air pollutants include tropospheric ozone (O3) and aerosols (small liquid or solid particles, also called PM2.5 when referring to particles with diameters of 2.5μm or less), which result mainly from emissions of methane (CH4), carbon monoxide (CO), nitrogen oxides (NOx), nonmethane volatile organics (NMVOCs), sulfur dioxide (SO2), ammonia (NH3), black carbon (BC), organic carbon (OC), and dust from human activities, such as energy production, industry, transportation, and agricultural and residential activities [2]. Emissions from natural sources, such as lightning NOx, NOx from soil, biogenic hydrocarbons, dimethyl sulfide (DMS) and sea salt from the oceans, as well as emissions from wild fires, also contribute to the formation of air pollutants.