Model sensitivity studies of the decrease in atmospheric carbon tetrachloride
Carbon tetrachloride (CCl<sub>4</sub>) is an ozone-depleting substance, which is controlled by the Montreal Protocol and for which the atmospheric abundance is decreasing. However, the current observed rate of this decrease is known to be slower than expected based on reported CCl<...
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| Language: | English |
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Copernicus Publications
2016-12-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/15741/2016/acp-16-15741-2016.pdf |
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| author | M. P. Chipperfield M. P. Chipperfield Q. Liang Q. Liang M. Rigby R. Hossaini S. A. Montzka S. Dhomse W. Feng W. Feng R. G. Prinn R. F. Weiss C. M. Harth P. K. Salameh J. Mühle S. O'Doherty D. Young P. G. Simmonds P. B. Krummel P. J. Fraser L. P. Steele J. D. Happell R. C. Rhew J. Butler S. A. Yvon-Lewis B. Hall D. Nance F. Moore B. R. Miller J. W. Elkins J. J. Harrison J. J. Harrison C. D. Boone E. L. Atlas E. Mahieu |
| author_facet | M. P. Chipperfield M. P. Chipperfield Q. Liang Q. Liang M. Rigby R. Hossaini S. A. Montzka S. Dhomse W. Feng W. Feng R. G. Prinn R. F. Weiss C. M. Harth P. K. Salameh J. Mühle S. O'Doherty D. Young P. G. Simmonds P. B. Krummel P. J. Fraser L. P. Steele J. D. Happell R. C. Rhew J. Butler S. A. Yvon-Lewis B. Hall D. Nance F. Moore B. R. Miller J. W. Elkins J. J. Harrison J. J. Harrison C. D. Boone E. L. Atlas E. Mahieu |
| author_sort | M. P. Chipperfield |
| collection | DOAJ |
| description | Carbon tetrachloride (CCl<sub>4</sub>) is an ozone-depleting substance, which is controlled by
the Montreal Protocol and for which the atmospheric abundance is decreasing.
However, the current observed rate of this decrease is known to be slower
than expected based on reported CCl<sub>4</sub> emissions and its estimated overall
atmospheric lifetime. Here we use a three-dimensional (3-D) chemical
transport model to investigate the impact on its predicted decay of
uncertainties in the rates at which CCl<sub>4</sub> is removed from the atmosphere
by photolysis, by ocean uptake and by degradation in soils. The largest sink
is atmospheric photolysis (74 % of total), but a reported 10 %
uncertainty in its combined photolysis cross section and quantum yield has
only a modest impact on the modelled rate of CCl<sub>4</sub> decay. This is partly
due to the limiting effect of the rate of transport of CCl<sub>4</sub> from the
main tropospheric reservoir to the stratosphere, where photolytic loss occurs.
The model suggests large interannual variability in the magnitude of this
stratospheric photolysis sink caused by variations in transport. The impact
of uncertainty in the minor soil sink (9 % of total) is also relatively
small. In contrast, the model shows that uncertainty in ocean loss (17 %
of total) has the largest impact on modelled CCl<sub>4</sub> decay due to its
sizeable contribution to CCl<sub>4</sub> loss and large lifetime uncertainty range
(147 to 241 years). With an assumed CCl<sub>4</sub> emission rate of
39 Gg year<sup>−1</sup>, the reference simulation with the best estimate of loss
processes still underestimates the observed CCl<sub>4</sub> (overestimates the
decay) over the past 2 decades but to a smaller extent than previous
studies. Changes to the rate of CCl<sub>4</sub> loss processes, in line with known
uncertainties, could bring the model into agreement with in situ surface and
remote-sensing measurements, as could an increase in emissions to around
47 Gg year<sup>−1</sup>. Further
progress in constraining the CCl<sub>4</sub> budget is partly limited by systematic
biases between observational datasets. For example, surface observations from
the National Oceanic and Atmospheric Administration (NOAA) network are larger
than from the Advanced Global Atmospheric Gases Experiment (AGAGE) network but have shown a
steeper decreasing trend over the past 2 decades. These differences imply a
difference in emissions which is significant relative to uncertainties in the
magnitudes of the CCl<sub>4</sub> sinks. |
| first_indexed | 2024-12-10T14:08:37Z |
| format | Article |
| id | doaj.art-44a333a0d6ad4eae9c8d7fa5b3feffde |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-10T14:08:37Z |
| publishDate | 2016-12-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-44a333a0d6ad4eae9c8d7fa5b3feffde2022-12-22T01:45:34ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242016-12-0116157411575410.5194/acp-16-15741-2016Model sensitivity studies of the decrease in atmospheric carbon tetrachlorideM. P. Chipperfield0M. P. Chipperfield1Q. Liang2Q. Liang3M. Rigby4R. Hossaini5S. A. Montzka6S. Dhomse7W. Feng8W. Feng9R. G. Prinn10R. F. Weiss11C. M. Harth12P. K. Salameh13J. Mühle14S. O'Doherty15D. Young16P. G. Simmonds17P. B. Krummel18P. J. Fraser19L. P. Steele20J. D. Happell21R. C. Rhew22J. Butler23S. A. Yvon-Lewis24B. Hall25D. Nance26F. Moore27B. R. Miller28J. W. Elkins29J. J. Harrison30J. J. Harrison31C. D. Boone32E. L. Atlas33E. Mahieu34School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UKNational Centre for Earth Observation, University of Leeds, Leeds, LS2 9JT, UKNASA Goddard Space Flight Center, Atmospheric Chemistry and Dynamics, Greenbelt, Maryland 20771, USAUniversities Space Research Association, GESTAR, Columbia, Maryland 21046, USAAtmospheric Chemistry Research Group, School of Chemistry, University of Bristol, Bristol, BS8 1TS, UKLancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UKGlobal Monitoring Division, NOAA Earth System Research Laboratory, Boulder, Colorado 80305, USASchool of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UKSchool of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UKNational Centre for Atmospheric Science, University of Leeds, Leeds, LS2 9JT, UKMassachusetts Institute of Technology, Cambridge, Massachusetts 02139 USAScripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0244, USAScripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0244, USAScripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0244, USAScripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0244, USAAtmospheric Chemistry Research Group, School of Chemistry, University of Bristol, Bristol, BS8 1TS, UKAtmospheric Chemistry Research Group, School of Chemistry, University of Bristol, Bristol, BS8 1TS, UKAtmospheric Chemistry Research Group, School of Chemistry, University of Bristol, Bristol, BS8 1TS, UKCSIRO Oceans and Atmosphere, Aspendale, Victoria 3195, AustraliaCSIRO Oceans and Atmosphere, Aspendale, Victoria 3195, AustraliaCSIRO Oceans and Atmosphere, Aspendale, Victoria 3195, AustraliaDepartment of Ocean Sciences, University of Miami, Florida 33149, USADepartmet of Geography, University of California, Berkeley, California 94720-4740, USAGlobal Monitoring Division, NOAA Earth System Research Laboratory, Boulder, Colorado 80305, USADepartment of Oceanography, Texas A&M University, College Station, Texas 77840, USAGlobal Monitoring Division, NOAA Earth System Research Laboratory, Boulder, Colorado 80305, USAGlobal Monitoring Division, NOAA Earth System Research Laboratory, Boulder, Colorado 80305, USAGlobal Monitoring Division, NOAA Earth System Research Laboratory, Boulder, Colorado 80305, USAGlobal Monitoring Division, NOAA Earth System Research Laboratory, Boulder, Colorado 80305, USAGlobal Monitoring Division, NOAA Earth System Research Laboratory, Boulder, Colorado 80305, USADepartment of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UKNational Centre for Earth Observation, University of Leicester, Leicester, LE1 7RH, UKDepartment of Chemistry, University of Waterloo, Ontario, N2L 3G1, CanadaDepartment of Atmospheric Sciences, University of Miami, Miami, Florida 33149, USAInstitute of Astrophysics and Geophysics, University of Liège, Liège 4000, BelgiumCarbon tetrachloride (CCl<sub>4</sub>) is an ozone-depleting substance, which is controlled by the Montreal Protocol and for which the atmospheric abundance is decreasing. However, the current observed rate of this decrease is known to be slower than expected based on reported CCl<sub>4</sub> emissions and its estimated overall atmospheric lifetime. Here we use a three-dimensional (3-D) chemical transport model to investigate the impact on its predicted decay of uncertainties in the rates at which CCl<sub>4</sub> is removed from the atmosphere by photolysis, by ocean uptake and by degradation in soils. The largest sink is atmospheric photolysis (74 % of total), but a reported 10 % uncertainty in its combined photolysis cross section and quantum yield has only a modest impact on the modelled rate of CCl<sub>4</sub> decay. This is partly due to the limiting effect of the rate of transport of CCl<sub>4</sub> from the main tropospheric reservoir to the stratosphere, where photolytic loss occurs. The model suggests large interannual variability in the magnitude of this stratospheric photolysis sink caused by variations in transport. The impact of uncertainty in the minor soil sink (9 % of total) is also relatively small. In contrast, the model shows that uncertainty in ocean loss (17 % of total) has the largest impact on modelled CCl<sub>4</sub> decay due to its sizeable contribution to CCl<sub>4</sub> loss and large lifetime uncertainty range (147 to 241 years). With an assumed CCl<sub>4</sub> emission rate of 39 Gg year<sup>−1</sup>, the reference simulation with the best estimate of loss processes still underestimates the observed CCl<sub>4</sub> (overestimates the decay) over the past 2 decades but to a smaller extent than previous studies. Changes to the rate of CCl<sub>4</sub> loss processes, in line with known uncertainties, could bring the model into agreement with in situ surface and remote-sensing measurements, as could an increase in emissions to around 47 Gg year<sup>−1</sup>. Further progress in constraining the CCl<sub>4</sub> budget is partly limited by systematic biases between observational datasets. For example, surface observations from the National Oceanic and Atmospheric Administration (NOAA) network are larger than from the Advanced Global Atmospheric Gases Experiment (AGAGE) network but have shown a steeper decreasing trend over the past 2 decades. These differences imply a difference in emissions which is significant relative to uncertainties in the magnitudes of the CCl<sub>4</sub> sinks.https://www.atmos-chem-phys.net/16/15741/2016/acp-16-15741-2016.pdf |
| spellingShingle | M. P. Chipperfield M. P. Chipperfield Q. Liang Q. Liang M. Rigby R. Hossaini S. A. Montzka S. Dhomse W. Feng W. Feng R. G. Prinn R. F. Weiss C. M. Harth P. K. Salameh J. Mühle S. O'Doherty D. Young P. G. Simmonds P. B. Krummel P. J. Fraser L. P. Steele J. D. Happell R. C. Rhew J. Butler S. A. Yvon-Lewis B. Hall D. Nance F. Moore B. R. Miller J. W. Elkins J. J. Harrison J. J. Harrison C. D. Boone E. L. Atlas E. Mahieu Model sensitivity studies of the decrease in atmospheric carbon tetrachloride Atmospheric Chemistry and Physics |
| title | Model sensitivity studies of the decrease in atmospheric carbon tetrachloride |
| title_full | Model sensitivity studies of the decrease in atmospheric carbon tetrachloride |
| title_fullStr | Model sensitivity studies of the decrease in atmospheric carbon tetrachloride |
| title_full_unstemmed | Model sensitivity studies of the decrease in atmospheric carbon tetrachloride |
| title_short | Model sensitivity studies of the decrease in atmospheric carbon tetrachloride |
| title_sort | model sensitivity studies of the decrease in atmospheric carbon tetrachloride |
| url | https://www.atmos-chem-phys.net/16/15741/2016/acp-16-15741-2016.pdf |
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