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Impacts of climate change, ozone recovery, and increasing methane on surface ozone and the tropospheric oxidizing capacity
Author(s) -
Morgenstern Olaf,
Zeng Guang,
Luke Abraham N.,
Telford Paul J.,
Braesicke Peter,
Pyle John A.,
Hardiman Steven C.,
O'Connor Fiona M.,
Johnson Colin E.
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2012jd018382
Subject(s) - ozone , atmospheric sciences , troposphere , environmental science , climatology , stratosphere , tropospheric ozone , northern hemisphere , ozone layer , greenhouse gas , methane , chemistry , geology , oceanography , organic chemistry
Using a stratosphere‐troposphere chemistry‐climate model, we compare the impacts of climate change, stratospheric ozone recovery, and methane increases on surface ozone and the tropospheric oxidizing capacity by 2050. Methane increases lead to a decreasing OH, particularly in the northern subtropics during summer. Stratospheric ozone recovery causes small increases of surface OH driven by increased stratosphere‐troposphere exchange, occurring during parts of the year in the southern extratropics. Tropospheric warming is also associated with increasing OH, maximizing in the Northern Hemisphere in northern summer. In combination, OH is anticipated to decrease by approximately 8% in the tropospheric average by 2050 in the scenario considered here. In conjunction with these changes to OH, we model substantial changes in surface ozone in both hemispheres. Methane increases alone will lead to increasing surface ozone by up to 2–3 ppbv in the zonal mean, maximizing around 30°N. This increase is exacerbated during austral winter when increased stratosphere‐troposphere flux of ozone causes an increase in surface ozone in the southern extratropics. Both increases are partially offset by decreases in surface ozone of up to 2 ppbv in the zonal mean, with substantial zonal asymmetries, due to global warming. We model substantial changes in the methane lifetime caused by the three factors. In the Arctic during summer, disappearing sea ice, in an ice‐albedo feedback, causes substantially reduced surface ozone. Of the three factors considered here, methane increases are found to exert the strongest influence on surface ozone.