<p>Due to the control of ozone (O<sub>3</sub>)-depleting substances (ODSs), it is believed that stratospheric O<sub>3</sub> will recover in the future. However, in the context of global change, the contributions of other factors to O<sub>3</sub> recovery are also worth discussing. This paper investigates the independent and joint influences of changes in global methane (CH<sub>4</sub>), carbon dioxide (CO<sub>2</sub>) and sea surface temperature (SST) on stratospheric O<sub>3</sub> under the Representative Concentration Pathway (RCP) 8.5 scenario in 2050 using sensitivity experiments with the Whole Atmosphere Community Climate Model, version 4. Results show that, in the polar lower stratosphere, CH<sub>4</sub> can reduce ODSs via chemical processes and further increase stratospheric O<sub>3</sub> and temperature, which tends to reduce polar stratospheric clouds. This acts as positive feedback to O<sub>3</sub> recovery. The increase of CH<sub>4</sub> in the sensitivity experiments (CH<sub>4</sub> is adjusted to match the 2050 levels under the RCP8.5 scenario) could lead to a polar O<sub>3</sub> recovery of about 27.9 DU in the Arctic. Increased CO<sub>2</sub> (CO<sub>2</sub> is adjusted to match the 2050 levels under the RCP8.5 scenario) can indirectly lead to a 6.5 DU increase in global total column O<sub>3</sub> (TCO) through radiative effects, while the influence of SST on TCO in tropical regions can reach −3.3%. For the joint impact of CH<sub>4</sub>, CO<sub>2</sub> and SST changes, CH<sub>4</sub> can account for up to 69.0% of the TCO variations in the Antarctic region. Finally, we compare the effects of CH<sub>4</sub> and ODSs on O<sub>3</sub> in the polar regions in future experiments based on the RCP8.5 scenario. We find that ODSs are a dominant factor in O<sub>3</sub> depletion in both poles; however, after 2040, the influence of increased CH<sub>4</sub> on O<sub>3</sub> recovery in the Arctic will surpass the effect of decreased ODSs. It implies that the future increase in CH<sub>4</sub> may have an important impact on O<sub>3</sub>.</p>

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Impact of Methane Emissions on Future Stratospheric Ozone Recovery

  • Na Liu,
  • Fei Xie,
  • Yan Xia,
  • Yingli Niu,
  • Hongwei Liu,
  • Xinyuan Xiang,
  • Yuanyuan Han

摘要

Due to the control of ozone (O3)-depleting substances (ODSs), it is believed that stratospheric O3 will recover in the future. However, in the context of global change, the contributions of other factors to O3 recovery are also worth discussing. This paper investigates the independent and joint influences of changes in global methane (CH4), carbon dioxide (CO2) and sea surface temperature (SST) on stratospheric O3 under the Representative Concentration Pathway (RCP) 8.5 scenario in 2050 using sensitivity experiments with the Whole Atmosphere Community Climate Model, version 4. Results show that, in the polar lower stratosphere, CH4 can reduce ODSs via chemical processes and further increase stratospheric O3 and temperature, which tends to reduce polar stratospheric clouds. This acts as positive feedback to O3 recovery. The increase of CH4 in the sensitivity experiments (CH4 is adjusted to match the 2050 levels under the RCP8.5 scenario) could lead to a polar O3 recovery of about 27.9 DU in the Arctic. Increased CO2 (CO2 is adjusted to match the 2050 levels under the RCP8.5 scenario) can indirectly lead to a 6.5 DU increase in global total column O3 (TCO) through radiative effects, while the influence of SST on TCO in tropical regions can reach −3.3%. For the joint impact of CH4, CO2 and SST changes, CH4 can account for up to 69.0% of the TCO variations in the Antarctic region. Finally, we compare the effects of CH4 and ODSs on O3 in the polar regions in future experiments based on the RCP8.5 scenario. We find that ODSs are a dominant factor in O3 depletion in both poles; however, after 2040, the influence of increased CH4 on O3 recovery in the Arctic will surpass the effect of decreased ODSs. It implies that the future increase in CH4 may have an important impact on O3.