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Despite many efforts to control anthropogenic sources, high ambient ozone (O _3 ) concentrations remain a serious air pollution problem in China. Terrestrial vegetation can remove surface O _3 through dry deposition but also enhance surface O _3 through biogenic volatile organic compound (BVOC) emissions. However, the net impacts of terrestrial vegetation on surface O _3 remains unclear. Here, we perform simulations using a chemistry-vegetation coupled model to assess the impacts of terrestrial vegetation on surface daily maximum 8 h average (MDA8) O _3 in China through biogeochemical processes, including BVOC emissions and stomatal uptake. The results show that vegetation biogeochemical processes increase summer mean surface MDA8 O _3 by 1.3 ppb in the present day in China, with 3.7 ppb from BVOC emissions but −2.7 ppb from stomatal uptake. However, the enhanced summer mean surface MDA8 O _3 from vegetation biogeochemical processes decreases from 5.4 to 2.7 ppb in the North China Plain (NCP), from 7.2 to 0.8 ppb in the Yangtze River Delta (YRD), from 8.7 to 1.8 ppb in the Sichuan Basin (SCB) and from 4.2 to 0.4 ppb in the Pearl River Delta by the period of carbon neutrality. Our study highlights that carbon neutrality-driven emission reductions can greatly mitigate the enhanced surface O _3 related to terrestrial vegetation, though there is still a positive impact of terrestrial vegetation on surface O _3 in some hotspots, including the NCP and the SCB.

To mitigate global warming and the resulting climate risk, many countries have accelerated the optimization of industrial structures and mixture of energy type in an attempt to achieve carbon neutrality by the second half of the 21st century. Here, we present the first assessment of the quantitative benefits of population exposure to extreme heat (defined by the heat index) during 2040–2049 under two scenarios of global carbon neutrality by 2060 and 2050, i.e. moderate green (MODGREEN) and strong green (STRGREEN) recovery scenarios, relative to the baseline scenario of Shared Socioeconomic Pathway (SSP) 2–4.5. Global mean extreme heat days increase by 12.1 d yr ^−1 (108%) during 2040–2049 under the SSP2-4.5 scenario relative to the historical period (1995–2014). The aggravating extreme heat events could be mitigated by as much as 12% and 18% during 2040–2049 under the MODGREEN and STRGREEN scenarios, respectively. Following the changes in extreme heat days, global population exposure to extreme heat is mitigated by 27.3 billion person-days (7%) in the MODGREEN scenario and 39.9 billion person-days (11%) in the STRGREEN scenario during 2040–2049 relative to the SSP2-4.5 scenario. Such benefits from these low-carbon policies are larger in regional hotspots, including India and Northern Africa, which have experienced high population growth and have extremely limited medical infrastructure. Moreover, an early carbon neutrality (2050 vs 2060) could avoid 12.6 billion person-days exposure to extreme heat during 2040–2049. Our results provide an important scientific support for governments to drive early policymaking for climate change mitigation.

The land ecosystems of China are estimated to provide an important sink for the increased atmospheric carbon dioxide (CO _2 ), but are undermined by severe ozone (O _3 ) pollution. Mitigation of O _3 damage to ecosystems remains a challenge considering that O _3 precursors are emitted from a wide range of anthropogenic sectors and O _3 formations are also affected by regional transport. Here, we combine chemical transport and dynamic vegetation models to quantify the benefits of sectoral and regional emission controls for the recovery of gross primary productivity (GPP) in the Yangtze River Delta (YRD). For sectoral emission controls, the largest mitigation of O _3 damage to GPP in YRD by 3.1 ± 0.4 and 2.2 ± 0.2 Gg[C] d ^−1 with 50% reductions in the emissions from industry and transportation sectors, respectively. For regional emission controls, reducing 50% anthropogenic emissions outside YRD can mitigate GPP losses by 18.6 ± 3.5 Gg[C] d ^−1 , larger than the recovery of 10.1 ± 1.6 Gg[C] d ^−1 by the 50% reductions of anthropogenic emissions within YRD. Moreover, summer months, especially July are the best period for GPP recovery from anthropogenic emission controls. Our results highlight the importance of sectoral and regional emission controls to mitigate O _3 damage to ecosystem productivities in YRD.

Frequent and severe PM _2.5 pollution over China seriously harms natural environment and human health. Changes in meteorological conditions in recent decades have been recognized to contribute to the long-term increase in PM _2.5 pollution in North China (NC). However, the dominant climatic factors driving the interdecadal changes of the weather conditions conducive to PM _2.5 pollution remain unclear. Here we identify a potential global teleconnection mechanism: the decadal reduction in European aerosol emissions since the 1980s may have partially contributed to the interdecadal increase in weather conditions conducive to PM _2.5 pollution in NC, measured by an Emission-weighted Air Stagnation Index (ASI _E ) that increases at a rate of 6.2% decade ^−1 (relative to the 1981–1985 level). By regression analysis, we show that the decreased European aerosol loadings can warm the lower atmosphere and induce anomalous ascending motion in Europe, which potentially stimulates two anomalous Rossby wave trains in the upper troposphere travelling eastward across Eurasia. The teleconnection patterns project on NC by weakening the near-surface horizontal dispersion, which may be favorable to the increase in local ASI _E and air pollution build-up. The suggested mechanism is further supported by the results from a set of large-ensemble simulations, showing that the European aerosol emission decline since the 1980s excites similar local heating and ascending motion and leads to increasing trends of 0.1–0.5 μ g m ^−3 (38 year) ^−1 in surface sulfate concentrations over most of NC. This proposed ‘West-to-East Aerosol-to-Aerosol’ teleconnection mechanism helps resolve opposite views on the impact of global versus local aerosol forcing on PM _2.5 pollution weather in NC. The policy implication is that the sustained decline in European aerosol emissions in coming decades, in conjunction with unabated global and regional warming, could further exacerbate air pollution in NC, thus imposing stronger pressure to reduce local emission sources quicker and deeper.