Ozone (O3) sits at the nexus of atmospheric and ecosystem science. As the most important air pollutant in many systems, O3 can affect ecosystem metabolism through its actions as an oxidant and climate via its impact as a greenhouse gas. Ozone can also affect radiative balance indirectly through its impacts on the biology underlying the production and consumption of other greenhouse gases. These indirect effects on radiative balance have received less attention on a large scale and have not yet been integrated into Earth System Science models. We present a meta-analytic synthesis of peer-reviewed literatures on experimentally-derived greenhouse gas flux responses to atmospheric O3 changes, and we then scale these response factors to estimate the greenhouse gas budget change globally. We focus on the three greenhouse gases with the largest biological fluxes from soils, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).
Results/Conclusions
Our synthesis suggests that elevated O3 promotes soil CO2 emission and strongly suppresses CH4 and N2O emissions. CH4 uptake in upland ecosystems is shown to be suppressed, but long-term O3 pressure tends to promote its uptake. We estimate the global net greenhouse gas budget change to be equivalent to approximately 30 Pg CO2 yr-1. The positive contribution of enhanced soil respiration is offset by suppressed CH4 and N2O fluxes, indicating the budget change by O3 is predominantly contingent on the alteration of terrestrial vegetation carbon sequestration capacity. Although there are uncertainties in determining the global budget change, our initial inspection represents a step forwards towards comprehensive understanding and evaluating of O3 pollution feedbacks to climate change. Future research should be conducted in many more different ecosystems around the world together with other global change agents, in particular in the context of ecosystem scale changes, and this work should seek collaboration between ecologists and atmospheric chemists in further addressing feedbacks of altered CH4 and N2O flux to the atmosphere O3 level.