P. K. Salameh's research while affiliated with University of California, San Diego and other places

Publications (115)

Article
Global emissions of the ozone-depleting gas HCFC-141b (1,1-dichloro-1-fluoroethane, CH3CCl2F) derived from measurements of atmospheric mole fractions increased between 2017 and 2021 despite a fall in reported production and consumption of HCFC-141b for dispersive uses. HCFC-141b is a controlled substance under the Montreal Protocol, and its phase-o...
Preprint
Global emissions of the ozone depleting gas 1,1-dichloro-1-fluoroethane (HCFC-141b, CH3CCl2F), derived from measurements of atmospheric mole fractions, have been rising between 2017–2021 despite a fall in reported production and consumption for dispersive uses. This study evaluates the possible drivers behind this renewed rise in emissions. HCFC-14...
Article
Methyl bromide (CH3Br) is a potent ozone-depleting substance (ODS) that has both natural and anthropogenic sources. CH3Br has been used mainly for preplant soil fumigation, post-harvest grain and timber fumigation, and structural fumigation. Most non-quarantine and pre-shipment (non-QPS) uses were phased out by 2005 for non-Article 5 (developed) co...
Article
Full-text available
Emissions of the potent greenhouse gas perfluorocyclobutane (c-C4F8, PFC-318, octafluorocyclobutane) into the global atmosphere inferred from atmospheric measurements have been increasing sharply since the early 2000s. We find that these inferred emissions are highly correlated with the production of hydrochlorofluorocarbon-22 (HCFC-22, CHClF2) for...
Preprint
Full-text available
Emissions of the potent greenhouse gas perfluorocyclobutane (c-C4F8, PFC-318, octafluorocyclobutane) into the global atmosphere inferred from atmospheric measurements have been increasing sharply since the early 2000s. We find that these inferred emissions are highly correlated with the production of hydrochlorofluorocarbon-22 (HCFC-22, CHClF2) for...
Preprint
Methyl bromide (CH3Br) is a potent ozone-depleting substance (ODS) that has both natural and anthropogenic sources. CH3Br has been used mainly for preplant soil fumigation, post-harvest grain and timber fumigation, and structural fumigation. Most non-quarantine/pre-shipment (non-QPS) uses have been phased-out in 2005 for non-Article 5 (developed) c...
Article
Full-text available
The perfluorocarbons (PFCs), tetrafluoromethane (CF4) and hexafluoroethane (C2F6), are potent greenhouse gases with very long atmospheric lifetimes. They are emitted almost entirely from industrial sources, including the aluminum and rare earth metal smelting industries that emit them as by‐products, and the semiconductor and flat panel display man...
Article
Full-text available
National greenhouse gas inventories (GHGIs) are submitted annually to the United Nations Framework Convention on Climate Change (UNFCCC). They are estimated in compliance with Intergovernmental Panel on Climate Change (IPCC) methodological guidance using activity data, emission factors and facility-level measurements. For some sources, the outputs...
Preprint
Full-text available
National Greenhouse Gas Inventories (GHGI) are submitted annually to the United Nations Framework Convention on Climate Change (UNFCCC). They are estimated in compliance with Intergovernmental Panel on Climate Change (IPCC) methodological guidance using activity data, emission factors and facility-level measurements. For some sources, the outputs f...
Article
Full-text available
The atmospheric concentration of trichlorofluoromethane (CFC-11) has been in decline since the production of ozone-depleting substances was phased out under the Montreal Protocol1,2. Since 2013, the concentration decline of CFC-11 slowed unexpectedly owing to increasing emissions, probably from unreported production, which, if sustained, would dela...
Article
Full-text available
Emissions of ozone-depleting substances, including trichlorofluoromethane (CFC-11), have decreased since the mid-1980s in response to the Montreal Protocol1,2. In recent years, an unexpected increase in CFC-11 emissions beginning in 2013 has been reported, with much of the global rise attributed to emissions from eastern China3,4. Here we use high-...
Article
Global and regional atmospheric measurements and modeling can play key roles in discovering and quantifying unexpected nascent emissions of environmentally important substances. We focus here on three hydrochlorofluorocarbons (HCFCs) that are restricted by the Montreal Protocol because of their roles in stratospheric ozone depletion. Based on measu...
Article
Full-text available
We report a 40-year history of SF6 atmospheric mole fractions measured at the Advanced Global Atmospheric Gases Experiment (AGAGE) monitoring sites, combined with archived air samples, to determine emission estimates from 1978 to 2018. Previously we reported a global emission rate of 7.3±0.6 Gg yr−1 in 2008 and over the past decade emissions have c...
Article
Full-text available
We present the organization, structure, instrumentation, and measurements of the Northeast Corridor greenhouse gas observation network. This network of tower-based in situ carbon dioxide and methane observation stations was established in 2015 with the goal of quantifying emissions of these gases in urban areas in the northeastern United States. A...
Preprint
Full-text available
Abstract. We report a 40-year history of SF<sub>6</sub> atmospheric mole fractions measured at the Advanced Global Atmospheric Gases Experiment (AGAGE) monitoring sites, combined with archived air samples to determine emission estimates from 1978–2018. Previously we reported a global emission rate of 7.3 ± 0.6 Gigagrams (Gg) yr<sup>−1</sup> in 2008...
Article
Full-text available
Under the Kigali Amendment to the Montreal Protocol, new controls are being implemented to reduce emissions of HFC-23 (CHF3), a by-product during the manufacture of HCFC-22 (CHClF2). Starting in 2015, China and India, who dominate global HCFC-22 production (75% in 2017), set out ambitious programs to reduce HFC-23 emissions. Here, we estimate that...
Conference Paper
Full-text available
We report on the development, performance evaluation, and field deployment of recently commercially available trace gas analyzers for the measurement of atmospheric methane and carbon dioxide. Based on Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS), the analyzers offer both the sensitivity and stability necessary for long-term a...
Preprint
Full-text available
Abstract. We present the organization, structure, instrumentation, and measurements of the Northeast Corridor greenhouse gas observation network. This network of tower-based in-situ carbon dioxide and methane observations was established in 2015 with the goal of quantifying emissions of these gases in urban areas in the north-eastern United States....
Article
Full-text available
We reconstruct atmospheric abundances of the potent greenhouse gas c-C4F8 (perfluorocyclobutane, perfluorocarbon PFC-318) from measurements of in situ, archived, firn, and aircraft air samples with precisions of ∼1 %–2 % reported on the SIO-14 gravimetric calibration scale. Combined with inverse methods, we found near-zero atmospheric abundances fr...
Article
Full-text available
The recovery of the stratospheric ozone layer relies on the continued decline in the atmospheric concentrations of ozone-depleting gases such as chlorofluorocarbons¹. The atmospheric concentration of trichlorofluoromethane (CFC-11), the second-most abundant chlorofluorocarbon, has declined substantially since the mid-1990s². A recently reported slo...
Article
Full-text available
We reconstruct atmospheric abundances of the potent greenhouse gas c-C4F8 (perfluorocyclobutane, perfluorocarbon PFC-318) from measurements of in situ, archived, firn, and aircraft air samples with precisions of ~ 1–2 % reported on the SIO-14 gravimetric calibration scale. Combined with inverse methods, we found near zero atmospheric abundances fro...
Article
Full-text available
Carbon tetrachloride (CCl4) is an ozone-depleting substance, accounting for about 10% of the chlorine in the troposphere. Under the terms of the Montreal Protocol, its production for dispersive uses was banned from 2010. In this work we show that, despite the controls on production being introduced, CCl4 emissions from the eastern part of China did...
Article
Full-text available
We present the organization, instrumentation, datasets, data interpretation, modeling, and accomplishments of the multinational global atmospheric measurement program AGAGE (Advanced Global Atmospheric Gases Experiment). AGAGE is distinguished by its capability to measure globally, at high frequency, and at multiple sites all the important species...
Article
Full-text available
High frequency measurements of trifluoromethane (HFC-23, CHF3), a potent hydrofluorocarbon greenhouse gas, largely emitted to the atmosphere as a by-product of the production of the hydrochlorofluorocarbon HCFC-22 (CHClF2), at five core stations of the Advanced Global Atmospheric Gases Experiment (AGAGE) network, combined with measurements on firn...
Article
Full-text available
A network of three tall tower measurement stations was set up in 2012 across the United Kingdom to expand measurements made at the long-term background northern hemispheric site, Mace Head, Ireland. Reliable and precise in situ greenhouse gas (GHG) analysis systems were developed and deployed at three sites in the UK with automated instrumentation...
Article
Full-text available
Based on observations of the chlorofluorocarbons CFC-13 (chlorotrifluoromethane), ΣCFC-114 (combined measurement of both isomers of dichlorotetrafluoroethane), and CFC-115 (chloropentafluoroethane) in atmospheric and firn samples, we reconstruct records of their tropospheric histories spanning nearly 8 decades. These compounds were measured in pola...
Article
Full-text available
We present the organization, instrumentation, datasets, data interpretation, modeling, and accomplishments of the multinational, global atmospheric measurement program AGAGE (Advanced Global Atmospheric Gases Experiment). AGAGE is distinguished by its capability to measure globally, at high frequency and multiple sites, all the important species in...
Article
Full-text available
A network of tall tower measurement stations was set up in 2012 across the United Kingdom to expand measurements made at the long-term background northern hemispheric site, Mace Head, Ireland. Reliable and precise in situ greenhouse gas (GHG) analysis systems were developed and deployed at three sites in the UK with automated custom-built instrumen...
Article
Full-text available
High frequency measurements of the potent hydrofluorocarbon greenhouse gas CHF3 (HFC-23), a by-product of production of the hydrochlorofluorocarbon HCFC-22 (CHClF2), at five core stations of the Advanced Global Atmospheric Gases Experiment (AGAGE) network, combined with measurements of firn and Cape Grim Air Archive (CGAA) air samples, are used to...
Preprint
Full-text available
Based on observations of three chlorofluorocarbons, CFC-13 (chlorotrifluoromethane), CFC-114 (dichlorotetrafluoroethane) and CFC-115 (chloropentafluoroethane) in atmospheric and firn samples, we reconstruct records of their tropospheric histories spanning nearly eight decades. These compounds were measured in polar firn air samples, in ambient air...
Article
Full-text available
We report continuous surface observations of carbon dioxide (CO2) and methane (CH4) from the Los Angeles (LA) Megacity Carbon Project during 2015. We devised a calibration strategy, methods for selection of background air masses, calculation of urban enhancements, and a detailed algorithm for estimating uncertainties in urban-scale CO2 and CH4 meas...
Article
Full-text available
The growth in global methane (CH4) concentration, which had been ongoing since the industrial revolution, stalled around the year 2000 before resuming globally in 2007. We evaluate the role of the hydroxyl radical (OH), the major CH4 sink, in the recent CH4 growth. We also examine the influence of systematic uncertainties in OH concentrations on CH...
Article
Full-text available
High-frequency, in situ global observations of HCFC-22 (CHClF2), HCFC-141b (CH3CCl2F), HCFC-142b (CH3CClF2) and HCFC-124 (CHClFCF3) and their main HFC replacements, HFC-134a (CH2FCF3), HFC-125 (CHF2CF3), HFC-143a (CH3CF3) and HFC-32 (CH2F2), have been used to determine their changing global growth rates and emissions in response to the Montreal Pro...
Article
Full-text available
Carbon tetrachloride (CCl4) 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 CCl4 emissions and its estimated overall atmospheric lifetime. Here we use a three-...
Article
Full-text available
High frequency, in situ global observations of HCFC-22 (CHClF2), HCFC-141b (CH3CCl2F), HCFC-142b (CH3CClF2) and HCFC-124 (CHClFCF3) and their main HFC replacements HFC-134a (CH2FCF3), HFC-125 (CHF2CF3), HFC-143a (CH3CF3), and HFC-32 (CH2F2) have been used to determine their changing global growth rates and emissions in response to the Montreal Prot...
Article
Full-text available
We report continuous surface observations of carbon dioxide (CO2) and methane (CH4) from the Los Angeles (LA) Megacity Carbon Project during 2015. We devised a calibration strategy, methods for selection of background air masses, calculation of urban enhancements, and a detailed algorithm for estimating uncertainties in urban scale CO2 and CH4 meas...
Article
We present an analysis of methane (CH4) emissions using atmospheric observations from thirteen sites in California during June 2013 – May 2014. A hierarchical Bayesian inversion method is used to estimate CH4 emissions for spatial regions (0.3° pixels for major regions) by comparing measured CH4 mixing ratios with transport model (WRF-STILT) predic...
Article
Full-text available
Carbon tetrachloride 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 CCl4 emissions and its estimated overall atmospheric lifetime. Here we use a three-dimensi...
Article
We report ground-based atmospheric measurements and emission estimates for the halons H-1211 (CBrClF2), H-1301 (CBrF3), and H-2402 (CBrF2CBrF2) from the AGAGE (Advanced Global Atmospheric Gases Experiment) and the NOAA (National Oceanic and Atmospheric Administration) global networks. We also include results from archived air samples in canisters a...
Article
High frequency, in situ observations from 11 globally distributed sites for the period 1994-2014 and archived air measurements dating from 1978 onward have been used to determine the global growth rate of 1,1-difluoroethane (HFC-152a, CH3CHF2). These observations have been combined with a range of atmospheric transport models to derive global emiss...
Article
Full-text available
High frequency, ground-based, in situ measurements from eleven globally-distributed sites covering 1994–2014, combined with measurements of archived air samples dating from 1978 onward and atmospheric transport models, have been used to estimate the growth of 1,1-difluoroethane (HFC-152a, CH3CHF2) mole fractions in the atmosphere and the global emi...
Article
Full-text available
We infer global and regional emissions of five of the most abundant hydrofluorocarbons (HFCs) using atmospheric measurements from the Advanced Global Atmospheric Gases Experiment and the National Institute for Environmental Studies, Japan, networks. We find that the total CO2-equivalent emissions of the five HFCs from countries that are required to...
Article
The potent anthropogenic perfluorocarbon greenhouse gases tetrafluoromethane (CF4) and hexafluoroethane (C2F6) are emitted to the atmosphere mainly by the aluminum and semiconductor industries. Global emissions of these perfluorocarbons (PFCs) calculated from atmospheric measurements are significantly greater than expected from reported national an...
Article
Full-text available
High-frequency, in situ observations from the Advanced Global Atmospheric Gases Experiment (AGAGE), for the period 2003 to 2012, combined with archive flask measurements dating back to 1977, have been used to capture the rapid growth of HFC-143a (CH3CF3) and HFC-32 (CH2F2) mole fractions and emissions into the atmosphere. Here we report the first i...
Article
High-frequency, in situ observations from the Advanced Global Atmospheric Gases Experiment (AGAGE), for the period 2003 to 2012, combined with archive flask measurements dating back to 1977, have been used to capture the rapid growth of HFC-143a (CH[subscript 3]CF[subscript 3]) and HFC- 32 (CH[subscript 2]F[subscript 2]) mole fractions and emission...
Article
Full-text available
We present a hierarchical Bayesian method for atmospheric trace gas inversions. This method is used to estimate emissions of trace gases as well as "hyper-parameters" that characterize the probability density functions (PDFs) of the a priori emissions and model-measurement covariances. By exploring the space of "uncertainties in uncertainties", we...
Article
Full-text available
Atmospheric measurements show that emissions of hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) are now the primary drivers of the positive growth in synthetic greenhouse gas (SGHG) radiative forcing. We infer recent SGHG emissions and examine the impact of future emissions scenarios, with a particular focus on proposals to reduce HF...
Article
We report in situ atmospheric measurements of HFC-43-10mee (C5H2F10, 1,1,1,2,2,3,4,5,5,5-decafluoropentane) from seven observatories at various latitudes, together with measurements of archived air samples and recent Antarctic flask air samples. The global mean tropospheric abundance was 0.21 ± 0.05 ppt (parts-per-trillion, dry air mole fraction) i...
Article
High frequency, in situ observations from the Advanced Global Atmospheric Gases Experiment (AGAGE), for the period 2003 to 2012, combined with archive flask measurements dating back to 1977, have been used to capture the rapid growth of HFC-143a (CH3CF3) and HFC-32 (CH2F2) mole fractions and emissions into the atmosphere. Here we report the first i...
Article
Full-text available
We present a hierarchical Bayesian method for atmospheric trace gas inversions. This method is used to estimate emissions of trace gases as well as "hyper-parameters" that characterize the probability density functions (PDF) of the a priori emissions and model-measurement covariances. By exploring the space of "uncertainties in uncertainties", we s...
Article
Full-text available
High-frequency atmospheric measurements of methane (CH4), nitrous oxide (N2O) and sulfur hexafluoride (SF6) from Darjeeling, India are presented from December 2011 (CH4)/March 2012 (N2O and SF6) through February 2013. These measurements were made on a gas chromatograph equipped with a flame ionization detector and electron capture detector, and wer...
Article
Since the Montreal Protocol on Substances that Deplete the Ozone Layer and its amendments came into effect, growth rates of the major ozone depleting substances (ODS), particularly CFC-11, -12 and -113 and CH[subscript 3]CCl[subscript 3], have declined markedly, paving the way for global stratospheric ozone recovery. Emissions have now fallen to re...
Article
Full-text available
High-frequency atmospheric measurements of methane (CH4), nitrous oxide (N2O) and sulfur hexafluoride (SF6) from Darjeeling, India are presented from December 2011 (CH4)/March 2012 (N2O and SF6) through February 2013. These measurements were made on a gas chromatograph equipped with a flame ionization detector and electron capture detector and were...