Very short-lived halogens amplify recent past and future ozone depleting trends in the tropical stratosphere

In contrast to the general stratospheric ozone recovery following international agreements recent observations show an ongoing net ozone depletion in the tropical lower stratosphere (LS). This depletion is thought to be driven by dynamical transport accelerated by global warming, while chemical processes have been considered to be unimportant

This work uses a chemistry-climate model to demonstrate that halogenated ozone-depleting very short-lived substances (VSLS) chemistry may account for around a quarter of the observed tropical LS negative ozone trend in 1998-2018. VSLS sources include both natural and anthropogenic emissions. Future projections show the persistence of the currently unaccounted for contribution of VSLS to ozone loss throughout the 21st century in the tropical LS, the only region of the global stratosphere not projecting an ozone recovery by 2100.

VSLS are not regulated within the Montreal Protocol, the international treaty that regulates the emissions of long-lived ozone depleting substances to protect the ozone layer. Our results demonstrate the need to include VSLS in the Montreal Protocol to mitigate their emissions in order to preserve the present and future ozone layer in low latitudes.

Julián Villamayor, Fernando Iglesias-Suarez, Carlos A. Cuevas, Rafael P. Fernandez, Qinyi Li, Marta Abalos, Ryan Hossaini, Martyn P. Chipperfield, Douglas E. Kinnison, Simone Tilmes, Jean-François Lamarque and Alfonso Saiz-Lopez. Very short-lived halogens amplify ozone depletion trends in the tropical lower stratosphere. Nature Climate Change. DOI: 10.1038/s41558-023-01671-y