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Title: Model sensitivity studies of the decrease in atmospheric carbon tetrachloride

Journal Article · · Atmospheric Chemistry and Physics (Online)
ORCiD logo [1];  [2];  [3];  [4];  [5];  [6];  [7];  [8];  [9];  [9];  [9]; ORCiD logo [9];  [3];  [3];  [3]; ORCiD logo [10];  [10];  [10];  [11];  [12] more »;  [5];  [13];  [5];  [5];  [5];  [5];  [5];  [14];  [15];  [16]; ORCiD logo [17] « less
  1. Univ. of Leeds (United Kingdom). School of Earth and Environment and National Centre for Earth Observation
  2. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Universities Space Research Association (GESTAR), Columbia, MD (United States)
  3. Univ. of Bristol (United Kingdom). Atmospheric Chemistry Research Group
  4. Lancaster Univ. (United Kingdom). Lancaster Environment Centre
  5. National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States). Earth System Research Lab.
  6. Univ. of Leeds (United Kingdom). School of Earth and Environment
  7. Univ. of Leeds (United Kingdom). School of Earth and Environment and National Centre for Atmospheric Science
  8. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  9. Univ. of California, San Diego, CA (United States). Scripps Institution of Oceanography
  10. Commonwealth Scientific and Industrial Research Organization (CSIRO) Oceans and Atmosphere, Aspendale VIC (Australia)
  11. Univ. of Miami, FL (United States). Dept. of Ocean Sciences
  12. Univ. of California, Berkeley, CA (United States). Dept. of Geography
  13. Texas A & M Univ., College Station, TX (United States). Dept. of Oceanography
  14. Univ. of Leicester (United Kingdom). Dept. of Physics and Astronomy; National Centre for Earth Observation
  15. Univ. of Waterloo, ON (Canada). Dept. of Chemistry
  16. Univ. of Miami, FL (United States). Dept. of Atmospheric Sciences
  17. Univ. of Liege (Belgium). Inst. of Astrophysics and Geophysics
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Carbon tetrachloride (CCl4) is an ozone-depleting substance, which is controlled by the Montreal Protocol and for which the atmospheric abundance is decreasing. But, the current observed rate of this decrease is known to be slower than expected based on reported CCl4 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 CCl4 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 CCl4 decay. This is partly due to the limiting effect of the rate of transport of CCl4 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 CCl4 decay due to its sizeable contribution to CCl4 loss and large lifetime uncertainty range (147 to 241 years). Furthermore, with an assumed CCl4 emission rate of 39 Gg year-1, the reference simulation with the best estimate of loss processes still underestimates the observed CCl4 (overestimates the decay) over the past 2 decades but to a smaller extent than previous studies. Changes to the rate of CCl4 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-1. Further progress in constraining the CCl4 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. The observed differences imply a difference in emissions which is significant relative to uncertainties in the magnitudes of the CCl4 sinks.

Research Organization:
Univ. of Leeds (United Kingdom). School of Earth and Environment
Sponsoring Organization:
USDOE; National Aeronautics and Space Administration (NASA)
Grant/Contract Number:
NE/J02449X/1; GA01103; ATM0849086; AGS0959853
OSTI ID:
1375403
Journal Information:
Atmospheric Chemistry and Physics (Online), Vol. 16, Issue 24; ISSN 1680-7324
Publisher:
European Geosciences UnionCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 5 works
Citation information provided by
Web of Science

References (28)

Global carbon tetrachloride distributions obtained from the Atmospheric Chemistry Experiment (ACE) journal January 2009
The Atmospheric Chemistry Experiment (ACE) journal January 2017
Trends in atmospheric halogen containing gases since 2004 journal November 2011
A comprehensive estimate for loss of atmospheric carbon tetrachloride (CCl4) to the ocean journal January 2016
New version of the TOMCAT/SLIMCAT off-line chemical transport model: Intercomparison of stratospheric tracer experiments journal April 2006
Multimodel estimates of atmospheric lifetimes of long-lived ozone-depleting substances: Present and future: Model Estimates of Atmospheric Lifetimes journal March 2014
The ERA-Interim reanalysis: configuration and performance of the data assimilation system journal April 2011
Emissions of carbon tetrachloride from Europe journal January 2016
Improving measurements of SF6 for the study of atmospheric transport and emissions journal January 2011
Soils: A global sink of atmospheric carbon tetrachloride: SOILS journal January 2003
A reassessment of the soil sink for atmospheric carbon tetrachloride based upon static flux chamber measurements journal June 2014
New and improved infra-red absorption cross sections and ACE-FTS retrievals of carbon tetrachloride (CCl 4 ) journal January 2017
Continued emissions of carbon tetrachloride from the United States nearly two decades after its phaseout for dispersive uses journal February 2016
Apparent removal of the transient tracer carbon tetrachloride from anoxic seawater journal November 1994
Constraining the carbon tetrachloride (CCl 4 ) budget using its global trend and inter-hemispheric gradient : THE CARBON TETRACHLORIDE BUDGET journal July 2014
Mean age of air and transport in a CTM: Comparison of different ECMWF analyses journal January 2007
In situ chloroform measurements at Advanced Global Atmospheric Gases Experiment atmospheric research stations from 1994 to 1998 journal September 2001
A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE journal July 2000
The atmospheric partial lifetime of carbon tetrachloride with respect to the global soil sink journal March 2016
Recent and future trends in synthetic greenhouse gas radiative forcing journal April 2014
Decrease of the carbon tetrachloride (CCl4) loading above Jungfraujoch, based on high resolution infrared solar spectra recorded between 1999 and 2011 journal July 2012
Global trends and emission estimates of CCl 4 from in situ background observations from July 1978 to June 1996 journal July 1998
Evaluation of simulated photolysis rates and their response to solar irradiance variability: Middle Atmosphere Photolysis Rate Modeling journal May 2016
Uncertainty analysis of projections of ozone-depleting substances: mixing ratios, EESC, ODPs, and GWPs journal January 2014
Emissions of ozone-depleting halocarbons from China: HALOCARBON EMISSIONS FROM CHINA journal August 2009
HIAPER Pole-to-Pole Observations (HIPPO): fine-grained, global-scale measurements of climatically important atmospheric gases and aerosols journal May 2011
HIPPO Combined Discrete Flask and GC Sample GHG, Halocarbon, and Hydrocarbon Data. Version 1.0 dataset January 2017
Atmospheric three-dimensional inverse modeling of regional industrial emissions and global oceanic uptake of carbon tetrachloride journal January 2010

Cited By (3)

Evaluating Oceanic Uptake of Atmospheric CCl 4 : A Combined Analysis of Model Simulations and Observations journal January 2019
Emissions of halocarbons from India inferred through atmospheric measurements journal January 2019
History of chemically and radiatively important atmospheric gases from the Advanced Global Atmospheric Gases Experiment (AGAGE) journal January 2018

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