Responses of ecosystem productivity to anthropogenic ozone and aerosols at 2060 under different emission scenarios

Anthropogenic emissions contribute a significant percentage to surface ozone (O3) and aerosols globally. The rate of plant photosynthesis, which represents the capability of terrestrial ecosystems to sequester carbon dioxide (CO2), is significantly affected by anthropogenic air pollutants. While the changes in anthropogenic emissions perturb atmospheric components, their consequent impacts on ecosystem productivity in the future climate remain unclear. Here, we apply a fully coupled climate-vegetation-chemistry model, ModelE2-YIBs, to explore the effects of O3 and aerosols from anthropogenic emissions on global gross primary productivity (GPP) under both present-day and different future emission scenarios at 2060. At the present day, anthropogenic air pollutants induce a GPP loss of -1.67 Pg[C] (-4%) in boreal summer with the contributions of -2.18 Pg[C] by O3 and +0.52 Pg[C] by aerosols. At 2060, the detrimental effect of air pollutants on GPP is exacerbated to -1.85 Pg[C] under a high emissions scenario but alleviated to -0.59 Pg[C] under a low emission scenario. The mitigated GPP loss in the latter scenario is owing to the effective control of anthropogenic emissions that on average reduces surface O3 concentrations by 8.14 ppbv globally relative to 2010. Although the CO2 fertilization effect is weaker in the low emission scenario, the strong decline in air pollutants brings additional GPP gains compared to the high scenario. Regionally, such GPP amelioration is close to or even outweighs the CO2 fertilization effect in eastern China and U.S., suggesting that the deep cut of anthropogenic emissions can effectively promote future ecosystem productivity through the reduction of O3 and aerosols over the nowadays polluted regions.