Evidence for a continuous decline in lower stratospheric ozone offsetting ozone layer recovery

Abstract

Abstract. Ozone forms in the Earth's atmosphere from the photodissociation of molecular oxygen, primarily in the tropical stratosphere. It is then transported to the extratropics by the Brewer-Dobson circulation (BDC), forming a protective "ozone layer" around the globe. Human emissions of halogen-containing ozone-depleting substances (hODSs) led to a decline in stratospheric ozone until they were banned by the Montreal Protocol, and since 1998 ozone in the upper stratosphere is rising again, likely the recovery from halogeninduced losses. Total column measurements of ozone between the Earth's surface and the top of the atmosphere indicate that the ozone layer has stopped declining across the globe, but no clear increase has been observed at latitudes between 60 • S and 60 • N outside the polar regions (60-90 • ). Here we report evidence from multiple satellite measurements that ozone in the lower stratosphere between 60 • S and 60 • N has indeed continued to decline since 1998. We find that, even though upper stratospheric ozone is recoverPublished by Copernicus Publications on behalf of the European Geosciences Union. 1380 W. T. Ball et al.: Continuous stratospheric ozone decline ing, the continuing downward trend in the lower stratosphere prevails, resulting in a downward trend in stratospheric column ozone between 60 • S and 60 • N. We find that total column ozone between 60 • S and 60 • N appears not to have decreased only because of increases in tropospheric column ozone that compensate for the stratospheric decreases. The reasons for the continued reduction of lower stratospheric ozone are not clear; models do not reproduce these trends, and thus the causes now urgently need to be established.

Representativeness of single lidar stations for zonally averaged ozone profiles, their trends and attribution to proxies

“…At least three recently published papers (Steinbrecht et al, 2017;Weber et al, 2018;Ball et al, 2018) show that total ozone and ozone profile trends are consistent with earlier WMO Scientific Assessment of Ozone Depletion (2014) findings. Despite the addition of four more years since WMO Scientific Assessment of Ozone Depletion (2014), Weber et al (2018) show that for most datasets and regions the trends in total ozone, since stratospheric halogens reached their maximum around 1997, are not significantly different from zero.…”

“…Due to improved datasets and longer records, the uncertainty in the profile trends reported by Steinbrecht et al (2017) was reduced by a factor of 2 compared to the estimates by Harris et al (2015). Moreover Ball et al (2018) provided solid evidence for a continuous ozone decline in the lower stratosphere capable of offsetting ozone recovery seen at the upper layers in the stratosphere.…”

Stratospheric ozone measurements at Arosa (Switzerland): history and scientific relevance

“…In the early 1980s, as new information about ozone chemistry reaction rate constants became available, it seemed that chemical ozone depletion by ODSs was considerably lower than had been predicted in the late 1970s (Benedick, 1991). However, in 1985 the Antarctic ozone hole was discovered (Farman et al, 1985) and the international ozone research community was able to demonstrate that the ozone hole was caused by the chlorine and bromine in halocarbons, which were largely of anthropogenic origin.…”

“…In the future, when the stratosphere is expected to gradually recover from the decreasing burden of ODSs, continued observations will not only be required to document the expected increase in stratospheric ozone, but also to document the effects of climate change on stratospheric ozone, as predicted to happen by CCMs, i.e. through enhancement of the Brewer-Dobson circulation and possible other effects connected with climate change (Ball et al, 2018).…”

Personalized UV Radiation Risk Monitoring Using Wearable Devices and Fuzzy Modeling

“…The most serious implication of UV radiation is known to be the main risk factor for many types of skin cancers such as squamous cell carcinoma [17]. To make matters worse, the ozone layer continuously declines over non-polar areas [18].…”