Numerical modeling of ozone damage to plants and its effects on atmospheric CO2 in China

Abstract

Tropospheric ozone (O3) is known to damage plant cells and suppress leaf photosynthesis, which can further reduce terrestrial carbon uptake and leave more carbon dioxide (CO2) in the atmosphere. While recent studies have assessed the effects of O3 on terrestrial carbon fluxes, the potential impacts on atmospheric CO2 concentrations have not been quantified. Here, we use a regional climate model (RegCM-CHEM4) coupled with the Yale Interactive terrestrial Biosphere model YIBs to estimate the effects of O3 exposure on atmospheric CO2 over China. Compared to simulations without O3 effects, sensitivity experiments with O3 damage show a significant reduction (12.1 ± 4.4%) in the gross primary productivity (GPP), up to 35% in summer. Meanwhile, terrestrial carbon sink is suppressed by 112.2 ± 22.5 Tg C for 2013 at the national level. Strong inhibitions of O3 on carbon fluxes are found in North, Northeast and South Central China, where O3 levels are high. Consequently, we find a significant increase in atmospheric CO2 concentrations due to O3-induced terrestrial carbon sink reduction. The increases of CO2 are more evident in the growing season. The maximum CO2 enhancement reaches as high as 6 ppm in Yunnan and Guizhou provinces. Our assessments indicate that tropospheric O3 has a detrimental impact on plant carbon uptake and leads to more CO2 accumulating in the atmosphere. Such impacts of O3 should be taken into account in global carbon cycle and future climate change.