Impact of Methane Emissions on Future Stratospheric Ozone Recovery
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Graphical Abstract
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Abstract
Due to the control of ozone-depleting substances (ODSs), it is believed that stratospheric ozone (O3) will recover in the future. However, in the context of global change, the contributions of other factors to ozone recovery are also worth discussing. Here, this paper investigates the independent and joint influence of changes in global methane (CH4), carbon dioxide (CO2), and sea surface temperature (SST) on stratospheric O3 under the RCP8.5 scenario in 2050 using sensitive experiments with the Whole Atmosphere Community Climate Model (WACCM). Results show that in the polar lower stratosphere, methane can reduce ozone-depleting substances via chemical processes and further increase stratospheric ozone and temperature which tends to reduce polar stratospheric clouds. This acts as positive feedback to ozone recovery. CH4 increase leads to polar ozone recovery of about 27.9DU in the Arctic. CO2 can indirectly lead to a 6.5DU increase in global 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% of the TCO variations in the Antarctic region. Using transient simulations (2005–2099) following different CH4 emissions, this paper further studies the impact of CH4 on future ozone recovery. These transient simulations indicate that the rate of ozone recovery increases with CH4 levels. In the Arctic, methane emission controlled under the RCP8.5 scenario may play a dominant role in stratospheric ozone recovery after 2040.
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