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Reimann, S, Elkins JW, Fraser PJ, Hall BD, Kurylo MJ, Mahieu E, Montzka SA, Prinn RG, Rigby M, Simmonds PG, Weiss RF.  2018.  Observing the atmospheric evolution of ozone-depleting substances. Comptes Rendus Geoscience. 350:384-392.   10.1016/j.crte.2018.08.008   AbstractWebsite

The atmospheric observations of ozone-depleting substances (ODSs) have been essential for following their atmospheric response to the production and use restrictions imposed by the Montreal Protocol and its Amendments and Adjustments. ODSs have been used since the first half of the 20th century in industrial and domestic applications. However, their atmospheric growth went unnoticed until the early 1970s, when they were discovered using gas chromatograph-electron capture detection (GC-ECD) instruments. Similar instrumentation formed the basis of global flask and in situ measurements commenced by NOAA and ALE/GAGE/AGAGE in the late 1970s. The combination of these networks, supported by a number of other laboratories, has been essential for following the tropospheric trends of ODSs. Additionally, ground-based remote sensing measurements within NDACC and aircraft-based observation programs have been crucial for measuring the evolution of the ODS abundances over the entire atmosphere. Maintaining these networks at least at their current state is vital for ensuring the on-going verification of the success of the Montreal Protocol. (C) 2018 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Meinshausen, M, Vogel E, Nauels A, Lorbacher K, Meinshausen N, Etheridge DM, Fraser PJ, Montzka SA, Rayner PJ, Trudinger CM, Krummel PB, Beyerle U, Canadell JG, Daniel JS, Enting IG, Law RM, Lunder CR, O'Doherty S, Prinn RG, Reimann S, Rubino M, Velders GJM, Vollmer MK, Wang RHJ, Weiss R.  2017.  Historical greenhouse gas concentrations for climate modelling (CMIP6). Geoscientific Model Development. 10:2057-2116.   10.5194/gmd-10-2057-2017   AbstractWebsite

Atmospheric greenhouse gas (GHG) concentrations are at unprecedented, record-high levels compared to the last 800 000 years. Those elevated GHG concentrations warm the planet and - partially offset by net cooling effects by aerosols - are largely responsible for the observed warming over the past 150 years. An accurate representation of GHG concentrations is hence important to understand and model recent climate change. So far, community efforts to create composite datasets of GHG concentrations with seasonal and latitudinal information have focused on marine boundary layer conditions and recent trends since the 1980s. Here, we provide consolidated datasets of historical atmospheric concentrations (mole fractions) of 43 GHGs to be used in the Climate Model Intercomparison Project Phase 6 (CMIP6) experiments. The presented datasets are based on AGAGE and NOAA networks, firn and ice core data, and archived air data, and a large set of published studies. In contrast to previous intercomparisons, the new datasets are latitudinally resolved and include seasonality. We focus on the period 1850-2014 for historical CMIP6 runs, but data are also provided for the last 2000 years. Weprovide consolidated datasets in various spatiotemporal resolutions for carbon dioxide (CO2), mcthanc (CH4) and nitrous oxide (N2O), as well as 40 other GHGs, namely 17 ozone-depleting substances, 11 hydrofluorocarbons (HFCs), 9 perfluorocarbons (PFCs), sulfur hexafluoride (SF6), nitrogen trifluoride (NF3) and sulfuryl fluoride (SO2F2). In addition we provide three equivalence species that aggregate concentrations of GHGs other than CO2, CH4 and N2O, weighted by their radiative forcing efficiencies. For the year 1850, which is used for pre-industrial control runs, we estimate annual global-mean surface concentrations of CO2 at 284.3 ppm, CH4 at 808.2 ppb and N2O at 273.0 ppb. The data are available at While the minimum CMIP6 recommendation is to use the global-and annual-mean time series, modelling groups can also choose our monthly and latitudinally resolved concentrations, which imply a stronger radiative forcing in the Northern Hemisphere winter (due to the latitudinal gradient and seasonality).

Vollmer, MK, Muhle J, Trudinger CM, Rigby M, Montzka SA, Harth CM, Miller BR, Henne S, Krummel PB, Hall BD, Young D, Kim J, Arduini J, Wenger A, Yao B, Reimann S, O'Doherty S, Maione M, Etheridge DM, Li SL, Verdonik DP, Park S, Dutton G, Steele LP, Lunder CR, Rhee TS, Hermansen O, Schmidbauer N, Wang RHJ, Hill M, Salameh PK, Langenfelds RL, Zhou LX, Blunier T, Schwander J, Elkins JW, Butler JH, Simmonds PG, Weiss RF, Prinn RG, Fraser PJ.  2016.  Atmospheric histories and global emissions of halons H-1211 (CBrClF2), H-1301 (CBrF3), and H-2402 (CBrF2CBrF2). Journal of Geophysical Research-Atmospheres. 121:3663-3686.   10.1002/2015jd024488   AbstractWebsite

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 National Oceanic and Atmospheric Administration global networks. We also include results from archived air samples in canisters and from polar firn in both hemispheres, thereby deriving an atmospheric record of nearly nine decades (1930s to present). All three halons were absent from the atmosphere until approximate to 1970, when their atmospheric burdens started to increase rapidly. In recent years H-1211 and H-2402 mole fractions have been declining, but H-1301 has continued to grow. High-frequency observations show continuing emissions of H-1211 and H-1301 near most AGAGE sites. For H-2402 the only emissions detected were derived from the region surrounding the Sea of Japan/East Sea. Based on our observations, we derive global emissions using two different inversion approaches. Emissions for H-1211 declined from a peak of 11ktyr(-1) (late 1990s) to 3.9ktyr(-1) at the end of our record (mean of 2013-2015), for H-1301 from 5.4ktyr(-1) (late 1980s) to 1.6ktyr(-1), and for H-2402 from 1.8ktyr(-1) (late 1980s) to 0.38ktyr(-1). Yearly summed halon emissions have decreased substantially; nevertheless, since 2000 they have accounted for approximate to 30% of the emissions of all major anthropogenic ozone depletion substances, when weighted by ozone depletion potentials.

Xiang, B, Patra PK, Montzka SA, Miller SM, Elkins JW, Moore FL, Atlas EL, Miller BR, Weiss RF, Prinn RG, Wofsy SC.  2014.  Global emissions of refrigerants HCFC-22 and HFC-134a: Unforeseen seasonal contributions. Proceedings of the National Academy of Sciences of the United States of America. 111:17379-17384.   10.1073/pnas.1417372111   AbstractWebsite

HCFC-22 (CHClF2) and HFC-134a (CH2FCF3) are two major gases currently used worldwide in domestic and commercial refrigeration and air conditioning. HCFC-22 contributes to stratospheric ozone depletion, and both species are potent greenhouse gases. In this work, we study in situ observations of HCFC-22 and HFC-134a taken from research aircraft over the Pacific Ocean in a 3-y span [Hlaper-Pole-to-Pole Observations (HIPPO) 2009-2011] and combine these data with long-term ground observations from global surface sites [ National Oceanic and Atmospheric Administration (NOAA) and Advanced Global Atmospheric Gases Experiment (AGAGE) networks]. We find the global annual emissions of HCFC-22 and HFC-134a have increased substantially over the past two decades. Emissions of HFC-134a are consistently higher compared with the United Nations Framework Convention on Climate Change (UNFCCC) inventory since 2000, by 60% more in recent years (2009-2012). Apart from these decadal emission constraints, we also quantify recent seasonal emission patterns showing that summertime emissions of HCFC-22 and HFC-134a are two to three times higher than wintertime emissions. This unforeseen large seasonal variation indicates that unaccounted mechanisms controlling refrigerant gas emissions are missing in the existing inventory estimates. Possible mechanisms enhancing refrigerant losses in summer are (i) higher vapor pressure in the sealed compartment of the system at summer high temperatures and (ii) more frequent use and service of refrigerators and air conditioners in summer months. Our results suggest that engineering (e. g., better temperature/vibration-resistant system sealing and new system design of more compact/efficient components) and regulatory (e. g., reinforcing system service regulations) steps to improve containment of these gases from working devices could effectively reduce their release to the atmosphere.

Rigby, M, Prinn RG, O'Doherty S, Miller BR, Ivy D, Muhle J, Harth CM, Salameh PK, Arnold T, Weiss RF, Krummel PB, Steele LP, Fraser PJ, Young D, Simmonds PG.  2014.  Recent and future trends in synthetic greenhouse gas radiative forcing. Geophysical Research Letters. 41:2623-2630.   10.1002/2013gl059099   AbstractWebsite

Atmospheric measurements show that emissions of hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons 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 HFC use under the Montreal Protocol. If these proposals are implemented, overall SGHG radiative forcing could peak at around 355mWm(-2) in 2020, before declining by approximately 26% by 2050, despite continued growth of fully fluorinated greenhouse gas emissions. Compared to no HFC policy projections, this amounts to a reduction in radiative forcing of between 50 and 240mWm(-2) by 2050 or a cumulative emissions saving equivalent to 0.5 to 2.8years of CO2 emissions at current levels. However, more complete reporting of global HFC emissions is required, as less than half of global emissions are currently accounted for.

Li, JL, Cunnold DM, Wang HJ, Weiss RF, Miller BR, Harth C, Salameh P, Harris JM.  2005.  Halocarbon emissions estimated from advanced global atmospheric gases experiment measured pollution events at Trinidad Head, California. Journal of Geophysical Research-Atmospheres. 110   10.1029/2004jd005739   AbstractWebsite

The emissions of halogenated gases from the West Coast region of the United States are estimated from measurements from 1995 to 2003 at the Advanced Global Atmospheric Gases Experiment site at Trinidad Head, California. The emissions estimation procedure uses pollution events combined with population densities integrated along back trajectories, and the estimates are constrained by independent estimates of CH4 and N2O emissions from the U. S. West Coast region. The best fit, average emissions of CH4 and N2O and the average chloroform emissions in California, Oregon, and Washington combined from 1996 to 2002 are 44, 3.7, and 0.07 kg person(-1) yr(-1), respectively. The emissions per person of CFC-11 (CCl3F), CFC-2 (CCl2F2), CFC-113 (CCl2FCClF2), and methyl chloroform (CH3CCl3) from California in 1996-1998 are calculated to be factors of approximately 2.2, 1.3, 0.7, and 1.6, respectively, less (more for CFC-113) than those reported for the northeastern United States by Barnes et al. (2003). The emission per person of all these gases in the U. S. West Coast region decreased from 1998 to 1999 by a factor of 2 or more, but from 1999 to 2002 the estimated emissions of all four gases have remained fairly constant and are 0.016, 0.048, 0.002, and 0.006 kg person(-1) yr(-1), respectively. The methyl chloroform estimates suggest a delay of up to 1 year in the decline of the emissions from 1996 to 1998, but otherwise, and in 1999-2000, in contrast to the Millet and Goldstein (2004) results, they are in agreement with the average methyl chloroform emissions per person for the United States based on the UNEP country by country consumption figures (A. McCulloch, private communication, 2004). Averaging the Trinidad Head and the Barnes et al. (2003) per person estimates and multiplying by the U. S. population suggests average methyl chloroform emissions in the United States of 18 Gg yr(-1) in 1996 to 1998. In 2001-2002, if the ratio of the emissions per person in these two regions was the same as in 1996-1998, we estimate U. S. emissions of 2.2 Gg yr(-1), which is one half of the Millet and Goldstein (2004) estimate.