Quantification of Stratospheric Ozone Recovery Due to Anthropogenic Halogens

Human release of CFCs and other ozone depleting substances (ODS) has led to a slow, steady erosion of the thickness of the global ozone layer over the past several decades. The ozone layer has begun to recover due to actions taken under the Montreal Protocol, which has led to a decrease in the atmospheric abundance of ozone depleting substances. Yet, unreported emissions of CFC-11 have led to a slower than expected decline, and there has been a rise in the atmospheric abundance of chlorinated very short lived (VSL) compounds not regulated under the Montreal Protocol.

In this presentation, we examine time series of ozone and halogens from a variety of observational platforms to quantify the attribution of the change in stratospheric ozone that is due to halogens. Our focus is on the extra-polar region: i.e., the state of the ozone layer between 55S and 55N where the vast majority of the world’s population resides. We will quantify the effect of continued release of CFC-11 and the presence of chlorinated VSL species on the recovery of the ozone layer. Additionally, we will use atmospheric observations to evaluate several proposed formulations for defining the quantity known as “Equivalent Effective Stratospheric Chlorine” (EESC) and assess the impact of these formulations on the projected recovery of the ozone layer.