Total ozone trends from 1979 to 2016 derived from five merged observational datasets – the emergence into ozone recovery

Abstract

Abstract.We report on updated trends using different merged datasets from satellite and groundbased observations for the time period 1979 until 2016. Trends were determined by application of a multiple linear regression (MLR) to annual mean zonal mean data. Merged datasets used are NASA MOD V8.6 and NOAA MERGE V8.6, both based upon data from the series of SBUV and SBUV-2 satellite instruments (1978-present) and the GTO (GOME-type Total Ozone) and GSG (GOME-SCIAMACHY-5 GOME2) merged datasets (1995-present) that are mainly composed of satellite data from GOME, SCIAMACHY, and GOME-2A. The fifth dataset are the monthly mean zonal mean data from ground data collected at WOUDC (World Ozone and UV Data Center). The addition of four more years of data since the last WMO Ozone Assessment (2013-2016 show that for most datasets and regions the trends since the stratospheric halogens reached maximum (∼1996 globally and ∼2000 in polar regions) are mostly not significantly different from zero. However, for some latitudes, in particular the southern hemisphere 10 extratropics and northern hemisphere subtropics, several datasets show small positive trends of slightly below +1 %/decade that are barely statistically significant at the 2σ uncertainty level. In the tropics only two datasets show significant trends of +0.5 to +0.8 %/decade, while the other show near zero trends. Positive trends since 2000 are observed over Antarctic in September, but near zero trends in October as well as in March over the Arctic. Since uncertainties due to possible drifts between the datasets as well as from the merging procedure used in the satellite datasets or due to the low sampling of ground 15 data are not accounted for, the retrieved trends can be only considered being at the brink of becoming significant, but there are indications that we are about to emerge into the expected recovery phase. Nevertheless, the recent trends are still considerably masked by the observed large year-to-year variability in total ozone.

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

“…Two recently published papers (Steinbrecht et al, 2017;Weber et al, 2017) show that total ozone and ozone profile trends are consistent with earlier WMO (2014) findings. Despite the addition of 4 more years since WMO 40 (2014), Weber et al (2017) 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.…”

“…Despite the addition of 4 more years since WMO 40 (2014), Weber et al (2017) 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. In the case of ozone profile trends, however, Steinbrecht et al (2017) confirmed increasing trends in the upper stratosphere (2 hPa) as first reported in WMO (2014).…”

“…A number of proxies have been used to explain the variability in space and time of the vertical ozone distribution, superimposed to the dominating annual cycle (Zerefos et al, 1992;Reinsel et al, 2002;Newchurch et al, 2003;Reinsel et al, 2005;Zanis et al, 2006;Nair et al, 2013;Frith et al, 2014;Harris et al, 2015;Steinbrecht et al, 2017;Weber et al, 2017;WMO 2007WMO , 2011WMO , 2014 influence in total ozone and its effect is confined in the upper troposphere/lower stratosphere (Zerefos et al, 1992). The Quasi Biennial Oscillation (QBO) is influencing ozone from the middle stratosphere down to the troposphere with a phase progressing both in height and latitude at rates of about 1 km per month vertically, and by about 4 degrees of latitude per month (Zerefos, 1983).…”

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

“…It is interesting to note here that the SBUV total column ozone non-linear trend initially increases from 1998 and then peaks around 2011, before decreasing. Frith et al (2014) and Weber et al (2017) found similar behaviour when applying linear trend fits to SBUV total column ozone, fixing the start date in January 2000 and incrementally increasing the end date, i.e. the largest positive trend was found for the period 2000-2011 and thereafter trends decreased.…”

“…However, non-polar (< 60 • ) total column ozone levels have remained stable since 2000 (WMO, 2014), with most latitudes displaying a positive, but non-significant, decadal trend (WMO, 2014). Results from Frith et al (2014) and Weber et al (2017) suggest a potential peak in positive trends around 2011, after which positive trends decreased, and while uncertainties shrink, significance remains elusive.…”