Natural halogens buffer tropospheric ozone in a changing climate

Iglesias-Suarez, Fernando and Badia, Alba and Fernandez, Rafael P. and Cuevas, Carlos A. and Kinnison, Douglas E. and Tilmes, Simone and Lamarque, Jean-François and Long, Mathew C. and Hossaini, Ryan and Saiz-Lopez, Alfonso (2020) Natural halogens buffer tropospheric ozone in a changing climate. Nature Climate Change, 2020. ISSN 1758-678X

Text (17006_3_merged_1575646716)
17006_3_merged_1575646716.pdf - Accepted Version
Download (984kB)

Abstract

Reactive atmospheric halogens destroy tropospheric ozone (O3), an air pollutant and greenhouse gas. The primary source of natural halogens is emissions from marine phytoplankton and algae, as well as abiotic sources from ocean and tropospheric chemistry, but how their fluxes will change under climate warming, and the resulting impacts on O3, are not well known. Here, we use an Earth system model to estimate that natural halogens deplete approximately 13% of tropospheric O3 in the present-day climate. Despite increased levels of natural halogens through the twenty-first century, this fraction remains stable due to compensation from hemispheric, regional and vertical heterogeneity in tropospheric O3 loss. Notably, this halogen-driven O3 buffering is projected to be greatest over polluted and populated regions, due mainly to iodine chemistry, with important implications for air quality.