This study evaluates the performance of a newly developed atmospheric chemistry-climate model, BCCAGCM_CUACE2.0 (Beijing Climate Center Atmospheric General Circulation Model_China Meteorological Administration Unified Atmospheric Chemistry Environment) model, for determining past (2010) and future (2050) tropospheric ozone (O-3) levels. The radiative forcing (RF), effective radiative forcing (ERF), and rapid adjustments (RAs, both atmospheric and cloud) due to changes in tropospheric O-3 are then simulated by using the model. The results show that the model reproduces the tropospheric O-3 distribution and the seasonal changes in O-3 surface concentration in 2010 reasonably compared with site observations throughout China. The global annual mean burden of tropospheric O-3 is simulated to have increased by 14.1 DU in 2010 relative to pre-industrial time, particularly in the Northern Hemisphere. Over the same period, tropospheric O-3 burden has increased by 21.1 DU in China, with the largest increase occurring over Southeast China. Although the simulated tropospheric O-3 burden exhibits a declining trend in global mean in the future, it increases over South Asia and Africa, according to the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios. The global annual mean ERF of tropospheric O-3 is estimated to be 0.25 W m(-2) in 1850-2010, and it is 0.50 W m(-2) over China. The corresponding atmospheric and cloud RAs caused by the increase of tropospheric O-3 are estimated to be 0.02 and 0.03 W m(-2), respectively. Under the RCP2.6, RCP4.5, RCP6.0, and RCP8.5 scenarios, the annual mean tropospheric O-3 ERFs are projected to be 0.29 (0.24), 0.18 (0.32), 0.23 (0.32), and 0.25 (0.01) W m-2 over the globe (China), respectively.

The spatial distribution, radiative forcing, and climatic effects of tropospheric ozone in China during summer were investigated by using the regional climate model RegCM4. The results revealed that the tropospheric ozone column concentration was high in East China, Central China, North China, and the Sichuan basin during summer. The increase in tropospheric ozone levels since the industrialization era produced clear-sky shortwave and clear-sky longwave radiative forcing of 0.18 and 0.71 W m(-2), respectively, which increased the average surface air temperature by 0.06 K and the average precipitation by 0.22 mm day(-1) over eastern China during summer. In addition, tropospheric ozone increased the land-sea thermal contrast, leading to an enhancement of East Asian summer monsoon circulation over southern China and a weakening over northern China. The notable increase in surface air temperature in northwestern China, East China, and North China could be attributed to the absorption of longwave radiation by ozone, negative cloud amount anomaly, and corresponding positive shortwave radiation anomaly. There was a substantial increase in precipitation in the middle and lower reaches of the Yangtze River. It was related to the enhanced upward motion and the increased water vapor brought by strengthened southerly winds in the lower troposphere.

This study simulates the effective radiative forcing (ERF) of tropospheric ozone from 1850 to 2013 and its effects on global climate using an aerosol-climate coupled model, BCC AGCM2.0.1 CUACE/Aero, in combination with OMI (Ozone Monitoring Instrument) satellite ozone data. According to the OMI observations, the global annual mean tropospheric column ozone (TCO) was 33.9 DU in 2013, and the largest TCO was distributed in the belts between 30A degrees N and 45A degrees N and at approximately 30A degrees S; the annual mean TCO was higher in the Northern Hemisphere than that in the Southern Hemisphere; and in boreal summer and autumn, the global mean TCO was higher than in winter and spring. The simulated ERF due to the change in tropospheric ozone concentration from 1850 to 2013 was 0.46 W m(-2), thereby causing an increase in the global annual mean surface temperature by 0.36A degrees C, and precipitation by 0.02 mm d(-1) (the increase of surface temperature had a significance level above 95%). The surface temperature was increased more obviously over the high latitudes in both hemispheres, with the maximum exceeding 1.4A degrees C in Siberia. There were opposite changes in precipitation near the equator, with an increase of 0.5 mm d(-1) near the Hawaiian Islands and a decrease of about -0.6 mm d(-1) near the middle of the Indian Ocean.

Black carbon (BC) aerosol and tropospheric ozone (O-3) are major air pollutants with short lifetimes of days to weeks in the atmosphere. These short-lived species have also made significant contributions to global warming since the preindustrial times (IPCC, 2013). Reductions in short-lived BC and tropospheric O-3 have been proposed as a complementary strategy to reductions in greenhouse gases. With the rapid economic development, concentrations of BC and tropospheric O-3 are relatively high in China, and therefore quantifying their roles in regional climate change is especially important. This review summarizes the existing knowledge with regard to impacts of BC and tropospheric O-3 on climate change in China and defines critical gaps needed to assess the climate benefits of emission control measures. Measured concentrations of BC and tropospheric O-3, optical properties of BC, as well as the model estimates of radiative forcing by BC and tropospheric O-3 are summarized. We also review regional and global modeling studies that have investigated climate change driven by BC and tropospheric O-3 in China; predicted sign and magnitude of the responses in temperature and precipitation to BC/O-3 forcing are presented. Based on the review of previous studies, research challenges pertaining to reductions in short-lived species to mitigate global warming are highlighted.

Tropospheric ozone (O-3) and aerosols are major air pollutants in the atmosphere. They have also made significant contributions to radiative forcing of climate since preindustrial times. With its rapid economic development, concentrations of air pollutants are relatively high in China; hence, quantifying the role of air pollutants in China in regional climate change is especially important. This review summarizes existing knowledge with regard to impacts of air pollutants on climate change in China and defines critical gaps needed to reduce the associated uncertainties. Measured monthly, seasonal, and annual mean surface-layer concentrations of O-3 and aerosols over China are compiled in this work, with the aim to show the magnitude of concentrations of O-3 and aerosols over China and to provide datasets for evaluation of model results in future studies. Ground-based and satellite measurements of O-3 column burden and aerosol optical properties, as well as model estimates of radiative forcing by tropospheric O-3 and aerosols are summarized. We also review regional and global modeling studies that have investigated climate change driven by tropospheric O-3 and/or aerosols in China; the predicted sign and magnitude of the responses in temperature and precipitation to O-3/aerosol forcings are presented. Based on this review, key priorities for future research on the climatic effects of air pollutants in China are highlighted.

The current state of studies on short-lived atmospheric constituents (greenhouse gases and aerosols) is reviewed. They have short atmospheric lifetimes (from several days to a few years) and can significantly affect the environment and climate. We propose reducing the emissions of these constituents as an alternative to the reduction of man-made carbon dioxide releases. We consider methane, hydrofluorocarbons, tropospheric ozone, and various aerosols (primarily, black carbon); discuss their atmospheric sources and destruction mechanisms; evaluate their content, atmospheric emissions, and climate impacts; and recommend efficient actions for the nearest future.

A unified chemistry-aerosol-climate model is applied in this work to compare climate responses to changing concentrations of long-lived greenhouse gases (GHGs, CO2, CH4, N2O), tropospheric O-3, and aerosols during the years 1951-2000. Concentrations of sulfate, nitrate, primary organic carbon (POA), secondary organic carbon (SOA), black carbon (BC) aerosols, and tropospheric O-3 for the years 1950 and 2000 are obtained a priori by coupled chemistry-aerosol-GCM simulations, and then monthly concentrations are interpolated linearly between 1951 and 2000. The annual concentrations of GHGs are taken from the IPCC Third Assessment Report. BC aerosol is internally mixed with other aerosols. Model results indicate that the simulated climate change over 1951-2000 is sensitive to anthropogenic changes in atmospheric components. The predicted year 2000 global mean surface air temperature can differ by 0.8 degrees C with different forcings. Relative to the climate simulation without changes in GHGs, O-3, and aerosols, anthropogenic forcings of SO42-, BC, BC+SO42-, BC+SO42 (-)+POA, BC+SO42- +POA+SOA+NO3-, O-3, and GHGs are predicted to change the surface air temperature averaged over 1971-2000 in eastern China, respectively, by -0.40 degrees C, +0.62 degrees C, +0.18 degrees C, +0.15 degrees C, -0.78 degrees C, +0.43 degrees C, and +0.85 degrees C, and to change the precipitation, respectively, by -0.21, +0.07, -0.03, +0.02, -0.24, -0.08, and +0.10 mm d(-1). The authors conclude that all major aerosols are as important as GHGs in influencing climate change in eastern China, and tropospheric O-3 also needs to be included in studies of regional climate change in China.

This study estimates direct radiative forcing by tropospheric ozone and all aerosols between the years 1850 and 2000, using the new IPCC AR5 (the Intergovernmental Panel on Climate Change Fifth Assessment Report) emissions inventories and a fully coupled chemistry-aerosol general circulation model. As compared to the previous Global Emissions Inventory Activity (GEIA) data, that have been commonly used for forcing estimates since 1990, the IPCC AR5 emissions inventories report lower anthropogenic emissions of organic carbon and black carbon aerosols and higher sulfur and NOx emissions. The simulated global and annual mean burdens of sulfate, nitrate, black carbon (BC), primary organic aerosol (POA), secondary organic aerosol (SOA), and ozone were 0.79, 0.35, 0.05, 0.49, 0.34, and 269 Tg, respectively, in the year 1850, and 1.90, 0.90, 0.11, 0.71, 0.32, and 377 Tg, respectively, in the year 2000. The estimated annual mean top of the atmosphere (TOA) direct radiative forcing of all anthropogenic aerosols based on the AR5 emissions inventories is -0.60 W m(-2) on a global mean basis from 1850 to 2000. However, this is -2.40 W m(-2) when forcing values are averaged over eastern China (18-45 degrees N and 95-125 degrees E). The value for tropospheric ozone is 0.17 W m(-2) on a global mean basis and 0.24 W m(-2) over eastern China. Forcing values indicate that the climatic effect of aerosols over eastern China is much more significant than the globally averaged effect.