scholarly journals Modelling the potential impacts of the recent, unexpected increase in CFC-11 emissions on total column ozone recovery

2020 ◽  
Vol 20 (12) ◽  
pp. 7153-7166
Author(s):  
James Keeble ◽  
N. Luke Abraham ◽  
Alexander T. Archibald ◽  
Martyn P. Chipperfield ◽  
Sandip Dhomse ◽  
...  
Keyword(s):  
Montreal Protocol ◽  
Total Column Ozone ◽  
The Road ◽  
The United Kingdom ◽  
Full Compliance ◽  
Rapid Action ◽  
On The Road ◽  
Column Ozone ◽  
The Impact ◽  
Total Column

Abstract. The temporal evolution of the abundance of long-lived, anthropogenic chlorofluorocarbons in the atmosphere is a major factor in determining the timing of total column ozone (TCO) recovery. Recent observations have shown that the atmospheric mixing ratio of CFC-11 is not declining as rapidly as expected under full compliance with the Montreal Protocol and indicate a new source of CFC-11 emissions. In this study, the impact of a number of potential future CFC-11 emissions scenarios on the timing of the TCO return to the 1960–1980 mean (an important milestone on the road to recovery) is investigated using the Met Office's Unified Model (Hewitt et al., 2011) coupled with the United Kingdom Chemistry and Aerosol scheme (UM-UKCA). Key uncertainties related to this new CFC-11 source and their impact on the timing of the TCO return date are explored, including the duration of new CFC-11 production and emissions; the impact of any newly created CFC-11 bank; and the effects of co-production of CFC-12. Scenario-independent relationships are identified between cumulative CFC emissions and the timing of the TCO return date, which can be used to establish the impact of future CFC emissions pathways on ozone recovery in the real world. It is found that, for every 200 Gg Cl (∼258 Gg CFC-11) emitted, the timing of the global TCO return to 1960–1980 averaged values is delayed by ∼0.56 years. However, a marked hemispheric asymmetry in the latitudinal impacts of cumulative Cl emissions on the timing of the TCO return date is identified, with longer delays in the Southern Hemisphere than the Northern Hemisphere for the same emission. Together, these results indicate that, if rapid action is taken to curb recently identified CFC-11 production, then no significant delay in the timing of the TCO return to the 1960–1980 mean is expected, highlighting the importance of ongoing, long-term measurement efforts to inform the accountability phase of the Montreal Protocol. However, if the emissions are allowed to continue into the future and are associated with the creation of large banks, then significant delays in the timing of the TCO return date may occur.

scholarly journals Modelling the potential impacts of the recent, unexpected increase in CFC-11 emissions on total column ozone recovery

2019 ◽  
Author(s):  
James Keeble ◽  
N. Luke Abraham ◽  
Alexander T. Archibald ◽  
Martyn P. Chipperfield ◽  
Sandip Dhomse ◽  
...  
Keyword(s):  
Montreal Protocol ◽  
Significant Delay ◽  
Total Column Ozone ◽  
Rapid Action ◽  
Emissions Scenarios ◽  
Column Ozone ◽  
The Impact ◽  
Long Term Measurement ◽  
Total Column

Abstract. The temporal evolution of long-lived, anthropogenic chlorofluorocarbons is a key control on the timing of total column ozone (TCO) recovery. Recent observations have shown that the atmospheric mixing ratio of CFC-11 is not declining as expected under complete compliance with the Montreal Protocol, and indicate a new source of CFC-11. In this study, the impact of a number of potential future CFC-11 emissions scenarios on TCO recovery is investigated using the UM-UKCA model. Key uncertainties related to this new CFC-11 source and their impact on the timing of TCO recovery are explored, including: the duration of new CFC-11 emissions/production; the impact of any newly created bank; and the effects of co-production of CFC-12. Scenario-independent relationships are identified between cumulative CFC emissions and the timing of ozone recovery, which can be used to establish the impact of future CFC emissions pathways on ozone recovery in the real world. It is found that, for every 200 Gg Cl emitted, the timing of global TCO recovery is delayed by ~ 0.56 years. However, a marked hemispheric asymmetry in the latitudinal impacts of cumulative Cl emissions on the timing of TCO recovery is identified, with longer delays in the southern hemisphere than the northern hemisphere for the same emission. Together, these results indicate that, if rapid action is taken to curb recently identified CFC-11 production then no significant delay in the timing of TCO recovery is expected, highlighting the importance of ongoing, long-term measurement efforts to inform the accountability phase of the Montreal Protocol. However, if the emissions are allowed to continue into the future, and are associated with the creation of large banks, then significant delays in the timing of TCO recovery may occur.

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 Options to accelerate ozone recovery:ozone and climate benefits

2010 ◽  
Vol 10 (4) ◽  
pp. 10839-10863
Author(s):  
J. S. Daniel ◽  
E. L. Fleming ◽  
R. W. Portmann ◽  
G. J. M. Velders ◽  
C. H. Jackman ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Total Ozone ◽  
Montreal Protocol ◽  
N2o Emissions ◽  
Total Column Ozone ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
The Impact ◽  
Total Column ◽  
Future Emissions

Abstract. Hypothetical reductions in future emissions of ozone-depleting substances (ODSs), including 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 that regulations already in force have had. If all anthropogenic ODS 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 ODS restrictions. Radiative forcing by 2100 would be about 0.23 W/m2 lower due to the elimination of N2O emissions and about 0.005 W/m2 lower due to destruction of the chlorofluorocarbon (CFC) bank. The ability of EESC to be a suitable metric for total ozone is also quantified. Responding to the recent suggestion that N2O should be considered an ODS, we provide an approach to incorporate N2O into the EESC formulation.

Decentralization in European and MENA Countries

2016 ◽  
pp. 1-27
Author(s):  
Francois Vaillancourt ◽  
Richard M. Bird
Keyword(s):  
National Unity ◽  
Mena Region ◽  
Mena Countries ◽  
Context Sensitive ◽  
The Road ◽  
The United Kingdom ◽  
Political Outcomes ◽  
Initial Question ◽  
On The Road ◽  
The Impact

The question considered in this chapter is whether decentralization is likely to hurt or help national unity in “countries at risk.” We begin with a literature review, focusing on three particular questions: the size and number of nations; the determinants of decentralization; and, finally, and bearing most directly on our topic, the links between decentralization and political outcomes. We next set out in capsule form some of the very mixed stories of linkages between decentralization and national unity found in Europe and the Middle East and North Africa (MENA) region, before considering more closely the ongoing discussions of secession in three European countries – Belgium, Spain and the United Kingdom. We conclude that the impact of decentralization on national unity is so complex and context-sensitive that no general answers to our initial question emerge: in some instances, decentralization may be an inducement for regions to stay in a country; in others, however, it may prove to be only a way station on the road to the exit.

scholarly journals Assessing the Impact of Clouds on UV-visible Total Column Ozone Measurements in the High Arctic

2018 ◽  
Author(s):  
Xiaoyi Zhao ◽  
Kristof Bognar ◽  
Vitali Fioletov ◽  
Andrea Pazmino ◽  
Florence Goutail ◽  
...  
Keyword(s):  
The Arctic ◽  
Total Column Ozone ◽  
Random Uncertainty ◽  
Screening Algorithm ◽  
Cloudy Weather ◽  
Column Ozone ◽  
The Impact ◽  
Cloud Screening ◽  
Total Column

Abstract. Zenith-Sky scattered light Differential Optical Absorption Spectroscopy (ZS-DOAS) has been used widely to retrieve total column ozone (TCO). ZS-DOAS measurements have the advantage of being less sensitive to clouds than direct-sun measurements. However, the presence of clouds still affects the quality of ZS-DOAS TCO. Clouds are thought to be the largest contributor to random uncertainty in ZS-DOAS TCO, but their impact on data quality still needs to be quantified. This study has two goals: (1) to study whether clouds have a significant impact on ZS-DOAS TCO, and (2) to develop a cloud-screening algorithm to improve ZS-DOAS measurements in the Arctic under cloudy conditions. To quantify the impact of weather, eight years of measured and modelled TCO have been used, along with information about weather conditions at Eureka, Canada (80.05° N, 86.41° W). Relative to direct-sun TCO measurements by Brewer spectrophotometers and modelled TCO, a positive bias is found in ZS-DOAS TCO measured in cloudy weather, and a negative bias is found for clear conditions, with differences of up to 5 % between clear and cloudy conditions. A cloud-screening algorithm is developed for high-latitudes using the colour index calculated from ZS-DOAS spectra. The quality of ZS-DOAS TCO datasets is assessed using a statistical uncertainty estimation model, which suggests a 3–4 % random uncertainty. The new cloud-screening algorithm reduces the random uncertainty by 0.6 %. If all measurements collected during cloudy conditions, as identified using the weather station observations, are removed, the random uncertainty is reduced by 1.3 %. This work demonstrates that clouds are a significant contributor to uncertainty in ZS-DOAS TCO and proposes a method that can be used to screen clouds in high-latitude spectra.

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 A study on harmonizing total ozone assimilation with multiple sensors

2018 ◽  
Author(s):  
Yves J. Rochon ◽  
Michael Sitwell ◽  
Young-Min Cho
Keyword(s):  
Bias Correction ◽  
Vertical Structure ◽  
Correlation Coefficients ◽  
Short Term ◽  
Total Column Ozone ◽  
Ozone Monitoring ◽  
Mean Differences ◽  
Column Ozone ◽  
The Impact ◽  
Total Column

Abstract. The impact of assimilating total column ozone datasets from single and multiple satellite data sources with and without bias correction has been examined with a version of the Environment and Climate Change Canada variational assimilation and forecasting system. The assimilated and evaluated data sources include the Global Ozone Monitoring Experiment-2 instruments on the MetOp-A and MetOp-B satellites (GOME-2A and GOME-2B), the total column ozone mapping instrument of the Ozone Mapping Profiler Suite (OMPS-NM) on the Suomi National Polar-orbiting Partnership (S-NPP) satellite, and the Ozone Monitoring Instrument (OMI) instrument on the Aura research satellite. Ground-based Brewer and Dobson spectrophotometers, and filter ozonometers, as well as the Solar Backscatter Ultraviolet satellite instrument (SBUV/2), served as independent validation sources for total column ozone. Regional and global mean differences of the OMI-TOMS data with measurements from the three ground-based instrument types for the three evaluated two month periods were found to be within 1 %, except for the polar regions with the largest differences from the comparatively small dataset in Antarctica exceeding 3 %. Values from SBUV/2 summed partial columns were typically larger than OMI-TOMS on average by 0.6 to 1.2 ± 0.7 %, with smaller differences than with ground-based over Antarctica. OMI-TOMS was chosen as the reference used in the bias correction instead of the ground-based observations due to OMI’s significantly better spatial and temporal coverage and interest in near-real time assimilation. Bias corrections as a function of latitude and solar zenith angle were performed with a two-week moving window using colocation with OMI-TOMS and three variants of differences with short-term forecasts. These approaches are shown to yield residual biases of less than 1 %, with the rare exceptions associated with bins with less data. These results were compared to a time-independent bias correction estimation that used colocations as a function of ozone effective temperature and solar zenith angle which, for the time period examined, resulted in larger changes in residual biases as a function of time for some cases. Assimilation experiments for the July-August 2014 period show a reduction of global and temporal mean biases for short-term forecasts relative to ground-based Brewer and Dobson data from a maximum of about 2.3 % in the absence of bias correction to less than 0.3 % in size when bias correction is included. Both temporally averaged and time varying mean differences of forecasts with OMI-TOMS are reduced to within 1 % for nearly all cases when bias corrected observations are assimilated for the latitudes where satellite data is present. The impact of bias correction on the standard deviations and anomaly correlation coefficients of forecast differences to OMI-TOMS is noticeable but small compared to the impact of introducing any total column ozone assimilation. The assimilation of total column ozone data can result in some improvement, as well as some deterioration, in the vertical structure of forecasts when comparing to Aura-MLS and ozonesonde profiles. The most significant improvement in the vertical domain from the assimilation of total column ozone alone is seen in the anomaly correlation coefficients in the tropical lower stratosphere, which increases from a minimum of 0.1 to about 0.6. Nonetheless, it is made evident that the quality of the vertical structure is most improved when also assimilating ozone profile data, which only weakly affects the total column short-term forecasts.

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