scholarly journals Ozone sensitivity to varying greenhouse gases and ozone-depleting substances in CCMI-1 simulations

2018 ◽  
Vol 18 (2) ◽  
pp. 1091-1114 ◽  
Author(s):  
Olaf Morgenstern ◽  
Kane A. Stone ◽  
Robyn Schofield ◽  
Hideharu Akiyoshi ◽  
Yousuke Yamashita ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Climate Model ◽  
Coupled Model ◽  
Model Ensemble ◽  
Total Column Ozone ◽  
Ozone Sensitivity ◽  
Intercomparison Project ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
Total Column

Abstract. Ozone fields simulated for the first phase of the Chemistry-Climate Model Initiative (CCMI-1) will be used as forcing data in the 6th Coupled Model Intercomparison Project. Here we assess, using reference and sensitivity simulations produced for CCMI-1, the suitability of CCMI-1 model results for this process, investigating the degree of consistency amongst models regarding their responses to variations in individual forcings. We consider the influences of methane, nitrous oxide, a combination of chlorinated or brominated ozone-depleting substances, and a combination of carbon dioxide and other greenhouse gases. We find varying degrees of consistency in the models' responses in ozone to these individual forcings, including some considerable disagreement. In particular, the response of total-column ozone to these forcings is less consistent across the multi-model ensemble than profile comparisons. We analyse how stratospheric age of air, a commonly used diagnostic of stratospheric transport, responds to the forcings. For this diagnostic we find some salient differences in model behaviour, which may explain some of the findings for ozone. The findings imply that the ozone fields derived from CCMI-1 are subject to considerable uncertainties regarding the impacts of these anthropogenic forcings. We offer some thoughts on how to best approach the problem of generating a consensus ozone database from a multi-model ensemble such as CCMI-1.

scholarly journals Ozone sensitivity to varying greenhouse gases and ozone-depleting substances in CCMI simulations

2017 ◽  
Author(s):  
Olaf Morgenstern ◽  
Hideharu Akiyoshi ◽  
Yousuke Yamashita ◽  
Douglas E. Kinnison ◽  
Rolando R. Garcia ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Climate Model ◽  
Phase 1 ◽  
Coupled Model ◽  
Total Column Ozone ◽  
Ozone Sensitivity ◽  
Intercomparison Project ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
Total Column

Abstract. Ozone fields simulated for the Chemistry-Climate Model Initiative (CCMI) will be used as forcing data in the 6th Coupled Model Intercomparison Project (CMIP6). Here we assess, using reference and sensitivity simulations produced for phase 1 of CCMI, the suitability of CCMI-1 model results for this process, investigating the degree of consistency amongst models regarding their responses to variations in individual forcings. We consider the influences of methane, nitrous oxide, a combination of chlorinated or brominated ozone-depleting substances (ODSs), and a combination of carbon dioxide and other greenhouse gases (GHGs). We find varying degrees of consistency in the models' responses in ozone to these individual forcings, including some considerable disagreement. In particular, the response of total-column ozone to these forcings is less consistent across the multi-model ensemble than profile comparisons. The likely cause of this is lower-stratospheric transport and dynamical responses exhibiting substantial inter-model differences. The findings imply that the ozone fields derived from CCMI-1 are subject to considerable uncertainties regarding the impacts of these anthropogenic forcings.

scholarly journals Antarctic ozone depletion between 1960 and 1980 in observations and chemistry–climate model simulations

2016 ◽  
Vol 16 (24) ◽  
pp. 15619-15627 ◽  
Author(s):  
Ulrike Langematz ◽  
Franziska Schmidt ◽  
Markus Kunze ◽  
Gregory E. Bodeker ◽  
Peter Braesicke
Keyword(s):  
Ozone Depletion ◽  
Climate Model ◽  
Total Column Ozone ◽  
Antarctic Ozone ◽  
Climate Model Simulations ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
The Antarctic ◽  
Total Column

Abstract. The year 1980 has often been used as a benchmark for the return of Antarctic ozone to conditions assumed to be unaffected by emissions of ozone-depleting substances (ODSs), implying that anthropogenic ozone depletion in Antarctica started around 1980. Here, the extent of anthropogenically driven Antarctic ozone depletion prior to 1980 is examined using output from transient chemistry–climate model (CCM) simulations from 1960 to 2000 with prescribed changes of ozone-depleting substance concentrations in conjunction with observations. A regression model is used to attribute CCM modelled and observed changes in Antarctic total column ozone to halogen-driven chemistry prior to 1980. Wintertime Antarctic ozone is strongly affected by dynamical processes that vary in amplitude from year to year and from model to model. However, when the dynamical and chemical impacts on ozone are separated, all models consistently show a long-term, halogen-induced negative trend in Antarctic ozone from 1960 to 1980. The anthropogenically driven ozone loss from 1960 to 1980 ranges between 26.4 ± 3.4 and 49.8 ± 6.2 % of the total anthropogenic ozone depletion from 1960 to 2000. An even stronger ozone decline of 56.4 ± 6.8 % was estimated from ozone observations. This analysis of the observations and simulations from 17 CCMs clarifies that while the return of Antarctic ozone to 1980 values remains a valid milestone, achieving that milestone is not indicative of full recovery of the Antarctic ozone layer from the effects of ODSs.

scholarly journals Diagnosing the radiative and chemical contributions to future changes in tropical column ozone with the UM-UKCA chemistry-climate model

2017 ◽  
Author(s):  
James Keeble ◽  
Ewa M. Bednarz ◽  
Antara Banerjee ◽  
N. Luke Abraham ◽  
Neil R. P. Harris ◽  
...  
Keyword(s):  
21St Century ◽  
Climate Model ◽  
Montreal Protocol ◽  
Total Column Ozone ◽  
Future Evolution ◽  
The Future ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
Total Column ◽  
Emissions Scenario

Abstract. Chemical and dynamical drivers of trends in tropical total column ozone (TCO3) for the recent past and future periods are explored using the UM-UKCA chemistry-climate model. A transient 1960-2100 simulation is analysed which follows the representative concentration pathway 6.0 (RCP6.0) emissions scenario for the future. Tropical averaged (10° S–10° N) TCO3 values decrease from the 1970s, reaching a minimum around 2000, and return to their 1980 values around 2040, consistent with the use and emission of ozone depleting substances (ODS), and their later controls under the Montreal Protocol. However, when the ozone column is subdivided into three partial columns (PCO3) that cover the upper stratosphere (PCO3US), lower stratosphere (PCO3LS) and troposphere (PCO3T), significant differences to the behaviour of the total column are seen. Modelled PCO3T values increase from 1960–2000 before remaining steady under this particular emissions scenario throughout the 21st century. PCO3LS values decrease rapidly from 1960–2000, remain steady until around 2050, before gradually decreasing further to 2100, never recovering to their 1980s values. PCO3US values decrease from 1960–2000, before rapidly increasing throughout the 21st century, recovering to 1980s values by ~ 2020, and are significantly higher than 1980s values by 2100. Using a series of idealised UM-UKCA time-slice simulations with varying concentrations of well-mixed greenhouse gases (GHG) and ODS set to either year 2000 or 2100 levels, we examine the main processes that drive the PCO3 responses in the three regions, and assess how these processes change under different emission scenarios. Finally, we present a simple, linearised model to describe the future evolution of tropical stratospheric column ozone values based on terms representing time-dependent abundances of GHG and ODS.

scholarly journals Attribution of observed changes in stratospheric ozone and temperature

2010 ◽  
Vol 10 (7) ◽  
pp. 17341-17367
Author(s):  
N. P. Gillett ◽  
H. Akiyoshi ◽  
S. Bekki ◽  
V. Eyring ◽  
R. Garcia ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Total Ozone ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Total Column Ozone ◽  
Detection And Attribution ◽  
Stratospheric Temperature ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
Total Column

Abstract. Three recently-completed sets of simulations of multiple chemistry-climate models with greenhouse gases only, with all anthropogenic forcings, and with anthropogenic and natural forcings, allow the causes of observed stratospheric changes to be quantitatively assessed using detection and attribution techniques. The total column ozone response to halogenated ozone depleting substances and to natural forcings is detectable and consistent in models and observations. However, the total ozone response to greenhouse gases in the models and observations appears to be inconsistent, which may be due to the models' inability to properly simulate tropospheric ozone changes. In the middle and upper stratosphere, simulated and observed SBUV/SAGE ozone changes are broadly consistent, and separate anthropogenic and natural responses are detectable in observations. The influence of ozone depleting substances and natural forcings can also be detected separately in observed lower stratospheric temperature, and the magnitudes of the simulated and observed responses to these forcings and to greenhouse gas changes are found to be consistent. In the mid and upper stratosphere the simulated natural and combined anthropogenic responses are detectable and consistent with observations, but the influences of greenhouse gases and ozone-depleting substances could not be separately detected in our analysis.

scholarly journals Attribution of observed changes in stratospheric ozone and temperature

2011 ◽  
Vol 11 (2) ◽  
pp. 599-609 ◽  
Author(s):  
N. P. Gillett ◽  
H. Akiyoshi ◽  
S. Bekki ◽  
P. Braesicke ◽  
V. Eyring ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Greenhouse Gas ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Total Column Ozone ◽  
Detection And Attribution ◽  
Stratospheric Temperature ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
Total Column

Abstract. Three recently-completed sets of simulations of multiple chemistry-climate models with greenhouse gases only, with all anthropogenic forcings, and with anthropogenic and natural forcings, allow the causes of observed stratospheric changes to be quantitatively assessed using detection and attribution techniques. The total column ozone response to halogenated ozone depleting substances and to natural forcings is detectable in observations, but the total column ozone response to greenhouse gas changes is not separately detectable. In the middle and upper stratosphere, simulated and observed SBUV/SAGE ozone changes are broadly consistent, and separate anthropogenic and natural responses are detectable in observations. The influence of ozone depleting substances and natural forcings can also be detected separately in observed lower stratospheric temperature, and the magnitudes of the simulated and observed responses to these forcings and to greenhouse gas changes are found to be consistent. In the mid and upper stratosphere the simulated natural and combined anthropogenic responses are detectable and consistent with observations, but the influences of greenhouse gases and ozone-depleting substances could not be separately detected in our analysis.

scholarly journals Options to accelerate ozone recovery: ozone and climate benefits

2010 ◽  
Vol 10 (16) ◽  
pp. 7697-7707 ◽  
Author(s):  
J. S. Daniel ◽  
E. L. Fleming ◽  
R. W. Portmann ◽  
G. J. M. Velders ◽  
C. H. Jackman ◽  
...  
Keyword(s):  
Ozone Depletion ◽  
Radiative Forcing ◽  
Montreal Protocol ◽  
N2o Emissions ◽  
Total Column Ozone ◽  
Potential Impact ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
The Impact ◽  
Total Column

Abstract. Hypothetical reductions in future emissions of ozone-depleting substances (ODSs) and N2O are evaluated in terms of effects on equivalent effective stratospheric chlorine (EESC), globally-averaged total column ozone, and radiative forcing through 2100. Due to the established success of the Montreal Protocol, these actions can have only a fraction of the impact on ozone depletion that regulations already in force have had. If all anthropogenic ODS and N2O emissions were halted beginning in 2011, ozone is calculated to be higher by about 1–2% during the period 2030–2100 compared to a case of no additional restrictions. Direct radiative forcing by 2100 would be about 0.23 W/m2 lower from the elimination of anthropogenic N2O emissions and about 0.005 W/m2 lower from the destruction of the chlorofluorocarbon (CFC) bank. Due to the potential impact of N2O on future ozone levels, we provide an approach to incorporate it into the EESC formulation, which is used extensively in ozone depletion analyses. The ability of EESC to describe total ozone changes arising from additional ODS and N2O controls is also quantified.

scholarly journals A global historical ozone data set and prominent features of stratospheric variability prior to 1979

2013 ◽  
Vol 13 (18) ◽  
pp. 9623-9639 ◽  
Author(s):  
S. Brönnimann ◽  
J. Bhend ◽  
J. Franke ◽  
S. Flückiger ◽  
A. M. Fischer ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Greenhouse Gases ◽  
Southern Oscillation ◽  
Observation Error ◽  
Quasi Biennial Oscillation ◽  
Data Set ◽  
Total Column Ozone ◽  
Ozone Data ◽  
Column Ozone ◽  
Total Column

Abstract. We present a vertically resolved zonal mean monthly mean global ozone data set spanning the period 1901 to 2007, called HISTOZ.1.0. It is based on a new approach that combines information from an ensemble of chemistry climate model (CCM) simulations with historical total column ozone information. The CCM simulations incorporate important external drivers of stratospheric chemistry and dynamics (in particular solar and volcanic effects, greenhouse gases and ozone depleting substances, sea surface temperatures, and the quasi-biennial oscillation). The historical total column ozone observations include ground-based measurements from the 1920s onward and satellite observations from 1970 to 1976. An off-line data assimilation approach is used to combine model simulations, observations, and information on the observation error. The period starting in 1979 was used for validation with existing ozone data sets and therefore only ground-based measurements were assimilated. Results demonstrate considerable skill from the CCM simulations alone. Assimilating observations provides additional skill for total column ozone. With respect to the vertical ozone distribution, assimilating observations increases on average the correlation with a reference data set, but does not decrease the mean squared error. Analyses of HISTOZ.1.0 with respect to the effects of El Niño–Southern Oscillation (ENSO) and of the 11 yr solar cycle on stratospheric ozone from 1934 to 1979 qualitatively confirm previous studies that focussed on the post-1979 period. The ENSO signature exhibits a much clearer imprint of a change in strength of the Brewer–Dobson circulation compared to the post-1979 period. The imprint of the 11 yr solar cycle is slightly weaker in the earlier period. Furthermore, the total column ozone increase from the 1950s to around 1970 at northern mid-latitudes is briefly discussed. Indications for contributions of a tropospheric ozone increase, greenhouse gases, and changes in atmospheric circulation are found. Finally, the paper points at several possible future improvements of HISTOZ.1.0.

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

2018 ◽  
Vol 18 (2) ◽  
pp. 1379-1394 ◽  
Author(s):  
William T. Ball ◽  
Justin Alsing ◽  
Daniel J. Mortlock ◽  
Johannes Staehelin ◽  
Joanna D. Haigh ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Ozone Layer ◽  
Montreal Protocol ◽  
Downward Trend ◽  
Polar Regions ◽  
Total Column Ozone ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
Total Column

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 halogen-induced 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 recovering, 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.

scholarly journals The 1985 southern hemisphere mid-latitude total column ozone anomaly

2007 ◽  
Vol 7 (3) ◽  
pp. 7137-7169
Author(s):  
G. E. Bodeker ◽  
H. Garny ◽  
D. Smale ◽  
M. Dameris ◽  
R. Deckert
Keyword(s):  
Southern Hemisphere ◽  
Atmospheric Chemistry ◽  
Climate Model ◽  
Transport Models ◽  
Quasi Biennial Oscillation ◽  
Total Column Ozone ◽  
Local Reduction ◽  
Column Ozone ◽  
Total Column

Abstract. One of the most significant events in the evolution of the ozone layer over southern mid-latitudes since the late 1970s was the large decrease observed in 1985. This event remains unexplained and most state-of-the-art atmospheric chemistry-transport models are unable to reproduce it. In this study, the 1985 southern hemisphere mid-latitude total column ozone anomaly is analyzed in detail based on observed daily total column ozone fields, stratospheric dynamical fields, and calculated diagnostics of stratospheric mixing. The 1985 anomaly appears to result from a combination of (i) an anomaly in the meridional circulation resulting from the westerly phase of the equatorial quasi-biennial oscillation (QBO), (ii) weaker transport of ozone from its tropical mid-stratosphere source across the sub-tropical barrier to mid-latitudes related to the particular phasing of the QBO with respect to the annual cycle, and (iii) a solar cycle induced local reduction in ozone. The results based on observations are compared and contrasted with analyses of ozone and dynamical fields from the ECHAM4.L39(DLR)/CHEM coupled chemistry-climate model (hereafter referred to as E39C). Equatorial winds in the E39C model are nudged towards observed winds between 10° S and 10° N and the ability of this model to produce an ozone anomaly in 1985, similar to that observed, confirms the role of the QBO in the anomaly.

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