Methane (CH4) is a greenhouse gas (GHG) with both anthropogenic and natural sources. It also contributes to air quality problems through its role in tropospheric ozone formation. Key source categories of anthropogenic CH4 emissions in Europe are the agricultural sector (~50 %), waste (~22 %), and energy (~15 %), which makes them the focus of intense research for developing mitigation actions. Stable isotope ratio measurement in CH4 provide the information needed to verify emissions by source type. To provide comparable and accurate atmospheric CH4 isotope ratios, there is an increasing need to develop metrological harmonized measurements protocols and procedures. In addition, there is a lack of a metrological infrastructure for source signature information needed to interpret atmospheric isotope ratio measurements, as well as an assessment of uncertainties in atmospheric transport models and inverse estimates of Europe's CH4 emissions.Here, we present the isoMET project that aims to (a) develop a harmonised in situ CH4 isotope dataset of ambient air in Europe to resolve compatibility issues of measurements of δ13C or δ2H in CH4 across multiple laboratories, b) develop a sustainable metrological infrastructure for a dataset for δ13C(CH4) and δ2H(CH4)-emissions source measurements in Europe and to evaluate the potential for source apportionment through clumped isotopes, c) use atmospheric chemistry transport modelling to inform the work in (a) and (b), creating estimates of the minimum measurement requirements for deployed instruments. References[1] isoMET project available at: https://www.npl.co.uk/21grd04-isomet[2] J. A. Nwaboh, J. Mohn, M. Fatima, T. Arnold, V. Ebert, Metrology for European emissions verification on methane isotopes (isoMET), CCQM GAWG-IRWG Workshop on Carbon Dioxide and Methane Stable Isotope Ratio Measurements, LATU (Uruguay), 2023Acknowledgements: The project 21GRD04 isoMET project has received funding from the European Partnership on Metrology, co-financed from the European Union’s Horizon Europe Research and Innovation Programme and by the Participating States. Empa has received funding from the Swiss State Secretaritat for Education, Research and Innovation (SERI).

It is estimated that global anthropogenic carbon dioxide (CO2) emissions reduced by up to 12% at the start of 2020 compared to recent years due to the COVID-19 related downturn in economic activity. Despite the large decrease in CO2 emissions, no reduction in the trend in background atmospheric CO2 concentrations has been detected. So, how long would it take for sustained COVID-19 CO2 emission reductions to be detected in daily and monthly averaged local CO2 concentration measurements? CO2 concentration measurements for five measurement sites in the UK and Ireland are combined with meteorological numerical weather prediction data to build statistical models that can predict future CO2 concentrations. It is found that 75% of the observed daily variability can be explained by these simple models. Emission reduction scenario experiments using these simple models illustrate that large daily and seasonal variability in local CO2 concentrations precludes the rapid emergence of a detectable signal. COVID-19 magnitude emissions reductions would only be detectable in the daily CO2 concentrations after at least 38 months and in monthly CO2 concentrations after 11 months of sustained reductions. For monthly CO2 concentrations the time of emergence is similar for all sites since the seasonal variability is largely driven by non-local fluxes of CO2 between the terrestrial biosphere and the atmosphere. The COVID-19 CO2 anthropogenic emissions reductions are similar in magnitude to those that are required to meet the Paris Agreement target of keeping global temperatures below 2° C. This study demonstrates that, using measurements alone, there will be a considerable lag between changes in global anthropogenic emissions and a detected signal in local CO2 concentration trends. Thus, there is likely to be a delay of several years between changes in policy designed to meet CO2 anthropogenic emissions targets and our ability to detect the impact of these policies on CO2 concentrations using atmospheric measurements alone.

Introduction Conclusions References

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.

Observations of methyl chloroform combined with an atmospheric transport model predict a Northern to Southern Hemisphere hydroxyl ratio of slightly less than 1, whereas commonly used atmospheric chemistry models predict ratios 15–45% higher.

Reproducible research is an increasingly important paradigm, and tools that support it are essential. Documentation for many SAS analytical products has long been created from a single-source system that embeds SAS ® code in L ATEX files and generates statistical results from those files. This system is now available to SAS users as an open-source package, which is similar in spirit to Sweave (Leisch 2002) and SASweave (Lenth 2007). The system automatically generates the SAS program file, which includes SAS macros that use the ODS document for capturing the output as external files. Listing and Graphic tags display the captured tabular and graphical output. This paper describes how to access and implement the package, and it illustrates typical usage with several examples.

Abstract. The first atmospheric observations and trends are presented for the high molecular weight perfluorocarbons (PFCs): decafluorobutane (C4F10), dodecafluoropentane (C5F12), tetradecafluorohexane (C6F14), hexadecafluoroheptane (C7F16) and octadecafluorooctane (C8F18). Their atmospheric histories are based on measurements of 38 Northern Hemisphere and 46 Southern Hemisphere archived air samples collected between 1973 to 2011 using the Advanced Global Atmospheric Gases Experiment (AGAGE) "Medusa" preconcentration gas chromatography-mass spectrometry systems. A new calibration scale was prepared for each PFC, with estimated accuracies of 6.8% for C4F10, 7.8% for C5F12, 4.0% for C6F14, 6.6% for C7F16 and 7.9% for C8F18. Based on our observations the 2011 globally averaged dry air mole fractions of these heavy PFCs are: 0.18 parts-per-trillion (ppt, i.e., parts per 1012) for C4F10, 0.12 ppt for C5F12, 0.28 ppt for C6F14, 0.12 ppt for C7F16 and 0.09 ppt for C8F18. These atmospheric mole fractions combine to contribute to a global average radiative forcing of 0.35 mW m−2, which is 3.6% of the total PFC radiative forcing. The globally averaged mean atmospheric growth rates of these PFCs during 1973–2011 are 4.58 parts per quadrillion (ppq, i.e., parts per 1015) per year (yr) for C4F10, 3.29 ppq yr−1 for C5F12, 7.50 ppq yr−1 for C6F14, 3.19 ppq yr−1 for C7F16 and 2.51 ppq yr−1 for C8F18. The growth rates of the heavy perfluorocarbons were largest in the early 1990s for C4F10 and C5F12 and in the mid-to-late 1990s for C6F14, C7F16 and C8F18. The more recent slow down in the growth rates of the high molecular weight PFCs suggests that emissions are declining as compared to the 1980s and 1990s. Nevertheless continued monitoring of these potent, extremely long-lived greenhouse gases is necessary to verify that global PFC emissions continue to decline.

Hydrogen in a hexapole collision cell is used with varying success in multi-collector Inductively Coupled Plasma Mass Spectrometry to reduce the plasma derived interferences Ar-40 O-16(+) and Ar-40 (OH+)-O-16 that are isobaric with Fe-56(+) and Fe-57(+) respectively. The reactions of ArO+ and ArOH+ with H-2 in the hexapole of a multi-collector Inductively Coupled Plasma Mass Spectrometer were studied practically and theoretically to better constrain possible reduction mechanisms. Addition of H-2 into the hexapole caused the signal of ArOH' to increase (+30%) suggesting its formation there. Reactions in the hexapole cell become dominant over transmission at a lower r.f. setting for ArOH+ than for ArO+, indicating that ArOH+ reacts more efficiently within the hexapole. Increasing H-2 flow rate caused a decrease in background equivalent concentrations of both ArO+ and ArOH+ with a lower ArOH+ decrease rate due to formation from (ArO+)-Ar-4:ArO+ + H-2 -> ArOH+ + H followed by ArOH+ + H-2 -> Ar + H2O+ + HAb initio calculations show ArO+ to have two low lying spin states; a quartet ((ArO+)-Ar-4) and low lying excited doublet ((ArO+)-Ar-2) that is likely to be metastable. Although highly exothermic (-538 kJ mol(-1)), reaction of (ArO+)-Ar-4 with H-2 to form H2O+ is spin forbidden. Formation of ArOH'from ArO' is exothermic (-26 kJ mol(-1) and -51 kJ mol(-1) from (ArO+)-Ar-4 and (ArO+)-Ar-2 respectively) and spin-allowed, supporting the formation of ArOH+ from ArO+ in the hexapole. The reaction ArOH+ + H-2 -> Ar + H2O+ + H (-39 kJ mol(-1) and -61 kJ mol(-1) from ArOH+ and 3 ArOH+ respectively) is likely the mechanism of ArOH+ removal. For 1ArOH(+) (possibly produced from (ArO+)-Ar-2) there may be a kinetic barrier for removal, giving a possible further explanation to the persistence of ArOH+. (c) 2008 Elsevier B.V. All rights reserved.