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The Montreal Protocol is successfully protecting the ozone layer. The main halogen gases responsible for stratospheric ozone depletion have been regulated under the Protocol, their combined atmospheric abundances are declining and ozone is increasing in some parts of the atmosphere1. Ozone depletion potentials2-4, relative measures of compounds' abilities to deplete stratospheric ozone, have been a key regulatory component of the Protocol in successfully guiding the phasing out in the manufacture of the most highly depleting substances. However, this latest, recovery phase in monitoring the success of the Protocol calls for further metrics. The 'delay in ozone return' has been widely used to indicate the effect of different emissions or phase-down strategies, but we argue here that it can sometimes be ambiguous or even of no use. Instead, we propose the use of an integrated ozone depletion (IOD) metric to indicate the impact of any new emission. The IOD measures the time-integrated column ozone depletion and depends only on the emission strength and the whole atmosphere and stratospheric lifetimes of the species considered. It provides a useful complementary metric of the impact of specific emissions of an ozone depleting substance for both the scientific and policy communities.

Póster presentado en: EGU General Assembly 2011 celebrada del 3 al 8 de abril en Viena, Austria. The Global Atmosphere Watch of WMO includes several stations in Antarctica that keep a close eye on the ozone layer during the ozone hole season. Observations made during the ozone holes from 2003 to 2010 will be compared to each other and interpreted in light of the meteorological conditions. Satellite observations will be used to get a more general picture of the size and depth of the ozone hole and will also be used to calculate various metrics for ozone hole severity. In 2003, 2005 and 2006, the ozone hole was relatively large with more ozone loss than normal. This is in particular the case for 2006, which by most ozone hole metrics was the most severe ozone holeon record. On the other hand, the ozone holes of 2004, 2007 and 2010 were less severe than normal, and only the very special ozone hole of 2002 had less ozone depletion when one regards the ozone holes of the last decade. The interannual variability will be discussed with the help of meteorological data, such as temperature conditions, possibility for polar stratospheric clouds, vortex shape and vortex longevity. Observations will also be compared to 3-D chemical transport model calculations.

Within the framework of the NDSC (Network for the Detection of Stratospheric Change) ground-based FTIR solar absorption spectra have been routinely recorded at Izaña Observatory (28° N, 16° W) on Tenerife Island since March 1999. By analyzing the shape of the absorption lines, and their different temperature sensitivities, the vertical distribution of the absorbers can be retrieved. Unique time series of subtropical profiles of O3, HCl, HF, N2O, and CH4 are presented. The effects of both dynamical and chemical annually varying trace gas cycles can be seen in the retrieved profiles. These include enhanced upwelling and photochemistry in summer and a more disturbed atmosphere in winter, which are typical of the subtropical stratosphere. A detailed error analysis has been performed for each profile. The output from two different three-dimensional (3-D) chemical transport models (CTMs), which are forced by ECMWF analyses, are compared to the measured profiles. Both models agree well with the measurements in tracking abrupt variations in the atmospheric structure, e.g. due to tropical streamers, in particular for the lower stratosphere. Simulated and measured profiles also reflect similar dynamical and chemical annual cycles. However, the differences between their mixing ratios clearly exceed the error bars estimated for the measured profiles. Possible reasons for this are discussed. We thank the Bundesministerium für Bildung und Forschung via the DLR by contracts 50EE0008 and 50EE0203 for funding

Nitrous oxide (N2O), like carbon dioxide, is a long-lived greenhouse gas that accumulates in the atmosphere. Over the past 150 years, increasing atmospheric N2O concentrations have contributed to stratospheric ozone depletion1 and climate change2, with the current rate of increase estimated at 2 per cent per decade. Existing national inventories do not provide a full picture of N2O emissions, owing to their omission of natural sources and limitations in methodology for attributing anthropogenic sources. Here we present a global N2O inventory that incorporates both natural and anthropogenic sources and accounts for the interaction between nitrogen additions and the biochemical processes that control N2O emissions. We use bottom-up (inventory, statistical extrapolation of flux measurements, process-based land and ocean modelling) and top-down (atmospheric inversion) approaches to provide a comprehensive quantification of global N2O sources and sinks resulting from 21 natural and human sectors between 1980 and 2016. Global N2O emissions were 17.0 (minimum–maximum estimates: 12.2–23.5) teragrams of nitrogen per year (bottom-up) and 16.9 (15.9–17.7) teragrams of nitrogen per year (top-down) between 2007 and 2016. Global human-induced emissions, which are dominated by nitrogen additions to croplands, increased by 30% over the past four decades to 7.3 (4.2–11.4) teragrams of nitrogen per year. This increase was mainly responsible for the growth in the atmospheric burden. Our findings point to growing N2O emissions in emerging economies—particularly Brazil, China and India. Analysis of process-based model estimates reveals an emerging N2O–climate feedback resulting from interactions between nitrogen additions and climate change. The recent growth in N2O emissions exceeds some of the highest projected emission scenarios3,4, underscoring the urgency to mitigate N2O emissions.

Gravity anomaly anomalies for 2015 and 2016

Gravity anomaly anomalies for 2015 and 2016

Precipitation anomalies calculated from TRMM (Tropical Rainfall Measuring Mission) (Huffman et al. 2007) version 7 and monthly daily maximum and minimum temperature from NOAA Climate Prediction Center (CPC) climatology (Fan et al. 2008).

Availability of atmospheric CO2 data used for atmospheric transport inversion calculations.

Table S1; Figures S1 and S5

Precipitation anomalies calculated from TRMM (Tropical Rainfall Measuring Mission) (Huffman et al. 2007) version 7 and monthly daily maximum and minimum temperature from NOAA Climate Prediction Center (CPC) climatology (Fan et al. 2008).

Table S1; Figures S1 and S5

Availability of atmospheric CO2 data used for atmospheric transport inversion calculations.

We have diagnosed the lifetimes of long lived source gases emitted at the surface and removed in the stratosphere using six three dimensional chemistry climate models (CCMs) and a two dimensional model. The models all used the same standard photochemical data. We investigate the effect of different definitions of lifetimes including running the models with both mixing ratio (MBC) and flux (FBC) boundary conditions. Within the same model the lifetimes diagnosed by different methods agree very well. Using FBCs versus MBCs leads to a different tracer burden as the implied lifetime contained in the MBC value does not necessarily match a model’s own calculated lifetime. In general there are much larger differences in the lifetimes calculated by different models the main causes of which are variations in the modelled rates of ascent and horizontal mixing in the tropical mid lower stratosphere. The model runs have been used to compute instantaneous and steady state lifetimes. For chlorofluorocarbons (CFCs) their atmospheric distribution was far from steady state in their growth phase through to the 1980s and the diagnosed instantaneous lifetime is accordingly much longer. Following the cessation of emissions the resulting decay of CFCs is much closer to steady state. For 2100 conditions the model circulation speeds generally increase but a thicker ozone layer due to recovery and climate change reduces photolysis rates. These effects compensate so the net impact on modelled lifetimes is small. For future assessments of stratospheric ozone use of FBCs would allow a consistent balance between rate of CFC removal and model circulation rate.

The satellite instrument SCIAMACHY was operational for almost 10 years during the period 2002-2012 aboard the Envisat of the ESA, measuring a number of important atmospheric trace gases in three different modes. SCIAMACHY measured the spectra of the solar light scattered by the atmosphere (or transmitted through the atmosphere in the occultation mode). These spectra were used to retrieve vertical profiles or total columns of the atmospheric trace gases as well as aerosol and cloud parameters. The purpose of this study was to investigate the spatio-temporal changes of stratospheric species such as ozone (O3) and nitrogen dioxide (NO2) and reveal possible drivers of the observed variations. Taking into account the importance of understanding the changes in the atmospheric composition it was crucial to 1) find an atmospheric model, which adequately describes chemical-dynamical processes in the stratosphere and 2) have an accurate knowledge of trace gases distribution.