Please read our news stories below.
June 2025
A Preprint edition of the project paper Harmonisation of methane isotope ratio measurements from different laboratories using atmospheric samples is now available on the EGU interactive community platform.
Establishing interlaboratory compatibility among measurements of stable isotope ratios of atmospheric methane (δ13C-CH4 and δD-CH4) is challenging. Significant offsets are common because laboratories have different ties to the VPDB or SMOW-SLAP scales. Umezawa et al. (2018) surveyed numerous comparison efforts for CH4 isotope measurements conducted from 2003 to 2017 and found scale offsets of up to 0.5 ‰ for δ13C-CH4 and 13 ‰ for δD-CH4 between laboratories. This exceeds the World Meteorological Organisation Global Atmospheric Watch (WMO-GAW) network compatibility targets of 0.02 ‰ and 1 ‰ considerably.
We employ a method to establish scale offsets between laboratories using their reported CH4 isotope measurements on atmospheric samples. Our study includes data from eight laboratories with experience in high-precision isotope ratio mass spectrometry (IRMS) measurements for atmospheric CH4. The analysis relies exclusively on routine atmospheric measurements conducted by these laboratories at high-latitude stations in the Northern and Southern Hemispheres, where we assume each measurement represents sufficiently well-mixed air at the latitude for direct comparison. We use two methodologies for interlaboratory comparisons: (I) assessing differences between time-adjacent observation data and (II) smoothing the observed data using polynomial and harmonic functions before comparison. The results of both methods are consistent, and with a few exceptions, the overall average offsets between laboratories align well with those reported by Umezawa et al. (2018). This indicates that interlaboratory offsets remain robust over multi-year periods. The evaluation of routine measurements allows us to calculate the interlaboratory offsets from hundreds, in some cases thousands of measurements. Therefore, the uncertainty in the mean interlaboratory offset is not limited by the analytical error of a single analysis but by real atmospheric variability between the sampling dates and stations. Using the same method, we assess this uncertainty by investigating measurements from four high-latitude sites analysed by the INSTAAR laboratory. After applying the derived interlaboratory offsets, we present a harmonised time series for δ13C-CH4 and δD-CH4 at high northern and southern latitudes, covering the period from 1988 to 2023.
The preprint has been put together by project colleagues Universiteit Utrecht, Ruprecht-Karls-Universitaet Heidelberg, Royal Holloway and Bedford New College and with the participation of interested parties from the Max-Planck-Institute for Biogeochemistry, Institute of Arctic and Alpine Research (INSTAAR), National Institute of Water and Atmospheric Research (NIWA) Center for Atmospheric and Oceanic Studies (Japan), NILU, National Institute of Polar Research (Japan), Jet Propulsion Laboratory – California and The Department of Chemistry - University of Cambridge.
May 2025
Colleagues from NIST, NPL, PTB and Empa have come together to produce a new paper. Developing calibration and measurement capabilities for atmospheric CH4 stable isotope ratios at NMIs/DIs: metrology for global comparability is available from Metrologia and is also available on our Documents page.
To establish robust calibration and measurement capabilities (CMCs) for atmospheric methane (CH4) stable isotope ratios, National Metrology Institutes (NMIs) and Designated Institutes (DIs) need a comprehensive understanding of the underlying measurement techniques, reference materials (RMs), calibration hierarchies, value assignment, uncertainty evaluation, and inter-laboratory comparison activities.
This review, developed by the CH4 Task Team within the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM) Gas Analysis Working Group (GAWG) and the Isotope Ratio Working Group (IRWG), provides key insights for developing these capabilities at NMIs/DIs. The World Meteorological Organization (WMO) recommended network compatibility goals for atmospheric methane stable isotope ratio monitoring, expressed as isotope delta values, are 0.02‰ for the stable carbon isotope delta (δ13C) value and 1‰ for the stable hydrogen isotope delta (δ2H) value, with extended targets of 0.2‰ for δ13C and 5‰ for δ2H. Global inter-laboratory comparisons have revealed offsets of up to 0.5‰ for δ13C and 13‰ for δ2H measurements, substantially exceeding the WMO targets.
To address these discrepancies, steady progress is being made, particularly by expert isotope laboratories, with increasing engagement from NMIs/DIs. Improved measurement techniques and the use of common RMs are bringing measurements closer to the WMO goals. This overview not only reviews the components necessary for establishing NMI/DI CMCs but also provides actionable recommendations to further align global measurements, including the development of standardized protocols, adoption of the VPDB carbon isotope delta scale for atmospheric data harmonization, and international comparison studies to support NMI/DIs in their CMC claims. These actions are critical for achieving long-term consistency and advancing global standards for atmospheric methane stable isotope ratio measurements.
January 2025
Colleagues from Empa, UU and PTB have come together to produce a new paper. Rapid High-Sensitivity Analysis of Methane Clumped Isotopes (Δ13CH3D and Δ12CH2D2) Using Mid-Infrared Laser Spectroscopy is available from Analytical Chemistry and is also available on our Documents page.
Mid-infrared laser absorption spectroscopy enables rapid and nondestructive analysis of methane clumped isotopes. However, current analytical methods require a sample size of 20 mL STP (0.82 mmol) of pure CH4 gas, which significantly limits its application to natural samples. To enhance the performance of spectroscopic measurement of methane clumped isotopes, we established a laser spectroscopic platform with newly selected spectral windows for clumped isotope analysis: 1076.97 cm–1 for 12CH2D2 and 1163.47 cm–1 for 13CH3D, and a custom-built gas inlet system. These spectral windows were identified through an extensive spectral survey on newly recorded high-resolution Fourier transform infrared (FTIR) spectra across the wavelength range of 870–3220 cm–1, thereby addressing gaps for 12CH2D2 in existing spectral databases.
In addition, we implemented several key technological advances, which result in superior control and performance of sample injection and analysis. We demonstrate that for small samples ranging from 3 to 10 mL (0.12–0.41 mmol) of CH4 gas, a measurement precision comparable to high-resolution isotope ratio mass spectrometry for Δ12CH2D2 (∼1.5‰) can be achieved through 3 to 8 repetitive measurements using a recycle-refilling system within a few hours. Samples larger than 10 mL can be quantified in under 20 min.
At the same time, for Δ13CH3D analysis a repeatability of 0.05‰, superior to mass spectrometry, was realized. These advancements in reducing sample size and shortening analysis time significantly improve the practicality of the spectroscopic technique for determining the clumped isotope signatures of natural methane samples, particularly for applications involving low CH4 concentrations or requiring consecutive analyses, which are feasible in conjunction with an automated preconcentration system.
12.09.24
Julia Wietzel and Martina Schmidt of project partner Universitaet Heidelberg recently provided two poster presentations.
Characterisation of δ13CH4 source signatures from methane sources in Germany with two different sampling strategies (Wietzel et al) and Detection and quantification of urban methane emissions in Heidelberg (Germany) using mobile and isotope measurements (Schmidt et al) were presented at the ICOS science conference 2024 in Versailles, France, 10th – 12th September.
The isoMet project was acknowledged in both posters.
Julia Wietzel ICOS 2024 poster
Martina Schmidt ICOS 2024 poster
21.08.24
Bibhasvata Dasgupta of project partner Universiteit Utrecht (above) recently provided an oral presentation. Harmonisation of atmospheric methane isotope ratio measurements from different laboratories: Procedures and Protocols was presented at the Goldschmidt 2024 Conference in Chicago which took place August 18th – 23rd at The Hilton Chicago.
Bibhasvata also conducted a workshop along with other speakers from the isotopologues community (above). IsoSchool aims to bridge the knowledge gap in stable isotope geochemistry by offering a two-day workshop focused on isotopologues of simple molecules with rare heavy isotopes, such as carbon (13C) and oxygen (17O or 18O). This workshop will cover methodologies, instruments, and applications in Earth Sciences, featuring lectures on clumped isotopes (Δ47, Δ48, Δ13CH3D, Δ12CH2D2) and the triple oxygen isotopic system.
Regarding the workshop, Bibhasvata says – ’We presented a synthesis of data from eight laboratories with experience in high-precision isotope ratio mass spectrometry (IRMS) measurements for CH₄ isotopes. The analysis relies exclusively on routine atmospheric measurements conducted at high-latitude stations in the Northern and Southern Hemispheres. The evaluation of routine measurements allows us to monitor interlaboratory offsets over time in addition to analytical and logistical methods of inter-calibration. After applying the overall interlaboratory offsets, we report a harmonized time series for δ¹³C-CH₄ and δD-CH₄ at high northern and southern latitudes, covering the period from 1988 to 2023’.
A link to IsoSchool can be found here.
08.08.24
Project partner NPL participated at the WMO/IAEA biannual meeting that was held at INPE, São Jose dos Campos, Brazil 5th – 8th August. Paul Brewer attended in person and Chris Rennick, Dafina Kikaj and Ruth Pearce participated online.
Four presentations were given on NPL work on measurement and traceability of greenhouse gases and tracers. These were Supporting the global measurement infrastructure and reporting values on a common scale presented by Paul Brewer, Direct high-precision radon quantification for interpreting high frequency greenhouse gas measurements presented by Dafina Kikaj, Measurements and calibration for high precision continuous monitoring of stable isotope ratios in atmospheric methane presented by Chris Rennick and Large-scale production of traceable Isotopic Methane Gas Reference Materials presented by Ruth Pearce.
Paul Brewer also led the discussion for updates to section 2 of the report on "Recommendations for the determination of uncertainty" in greenhouse gas measurements.
03.07.24
Sara Defratyka of project partner NPL, gave an invited talk to the isoNET network, in our progress toward understanding Δ13CH3D and Δ12CH2D2. The seminar Development of automated preconcentrator to measure clumped isotopologues of methane (Δ13CH3D and Δ12CH2D2) from the atmosphere and sources was held online on the 3rd July.
12.04.24
Sara Defratyka of project partner NPL, provided a training course on the project at the ULTRA User meeting, held by the International Centre for Isotope Effects Research (ICIER), Nanjing University, China 12th April 2024. Sara’s training session focussed on the preconcentrator system at NPL for Δ13CH3D and Δ12CH2D2.
07.05.24
Bibhasvata Dasgupta (right) of project partner Universiteit Utrecht recently provided a poster presentation. Harmonisation of atmospheric methane isotope ratio measurements from different laboratories: Procedures and Protocols was presented at the BASIS Symposium 2024 which took place April 25th – 26th at the Congress Centre Amsterdam Science Park.
As atmospheric trace gas isotope measurements get more common and analytical techniques become more diverse, combining, and merging observational records is challenging because of significant offsets between measurements from different laboratories. To address calibration challenges in atmospheric science, we need to standardise calibration procedures, conduct regular inter-laboratory comparisons, provide adequate training and education, use accurately characterised reference materials, continuously improve calibration procedures, and encourage collaboration and communication between laboratories and research institutions. The most recent worldwide comparison among laboratories, concentrating specifically on the IRMS measurement method and encompassing analyses carried out from 2003 to 2017, revealed disparities of up to 0.5 ‰ for δ13C and 13 ‰ for δ2H isotope ratio measurements in ambient air samples. These differences are equivalent to 25 and 13 times the compatibility targets set by the WMO-GAW network, respectively.
BASIS (Benelux Association for Stable Isotope Scientists) originated from the previous Benelux Isotope Group (BIG), a group of active scientists that organized annual meetings without a formal organisation. BIG started in 2000 as an Isotope Ratio Mass Spectrometry (IRMS) users group and has gathered every year since.
01.05.24
A successful M18 meeting for the isoMET project was held online by project partner PTB at the General Assembly 2024 of the European Geosciences Union (EGU) in Vienna, Austria in April. Javis Nwaboh (PTB) coordinator of the project and welcomed all to the meeting. This was followed by presentations on work progressed under WP1 (Developing a harmonised in situ CH4 isotope dataset of ambient air in Europe) by Javis Nwaboh and associated partners NPL, TUBITAK, Empa, UU, The University of Glasgow, VTT, Royal Holloway and Bedford New College, UHEI, Université De Versailles Saint-Quentin-En-Yvelines and Stockholms Universitet. Presentations on work progressed under WP2 (A sustainable metrological infrastructure for a dataset for CH4 isotope source signature measurements in Europe) were provided by Joachim Mohn, (Empa) and associated partners NPL, TUBITAK, PTB, Universiteit Utrecht, The University of Glasgow, VTT, Royal Holloway and Bedford New College, Ruprecht-Karls-Universitaet Heidelberg, Université De Versailles Saint-Quentin-En-Yvelines and The University of Bristol.
For WP3 (Atmospheric transport modelling to direct the measurement strategy for optimal emissions estimation and demonstration of emissions estimates from new datasets) progress was presented to the consortium by Tim Arnold (NPL) and associated partners The University of Bristol and Empa.
Presentations on work progressed under WP4 (Creating impact) were provided by Mehr Fatima (VTT). Javis Nwaboh (PTB) provided updates on WP5 (Management and coordination). During the work package presentations and discussions, there was further discussion with the consortium regarding the output of the project and future progress towards M27.
01.05.24
The project was well represented by many of the partners at the recent General Assembly 2024 of the European Geosciences Union (EGU) held at the Austria Center Vienna (ACV) in Vienna, Austria.
Arranged by the partners, Session AS3.40 invited contributions from the community working on the use of isotope ratios and other tracers in understanding the sources/ sinks of GHGs to the atmosphere. The session looked at:
Posters from the project presented at EGU24 from the project included:
Naizhong Zhang (above) of project partner Empa presented on the Pros and cons of methane clumped isotope analysis by high-resolution isotope-ratio mass spectrometry and laser absorption spectroscopy.
Bibhasvata Dasgupta (right) of project partner Universiteit Utrecht also presented at the EGU on the use of methane isotope measurements to constrain regional scale emissions.
The European Geosciences Union (EGU) is the leading organisation for Earth, planetary and space science research in Europe. With partner organisations worldwide, the EGU fosters fundamental geoscience research, alongside applied research that addresses key societal and environmental challenges. The EGU vision is to realise a sustainable and just future for humanity and for the planet.
March 24
Colleagues from NPL have produced a new paper. Fractionation of Methane Isotopologues during Preparation for Analysis from Ambient Air is available from Analytical Chemistry and is also available on our Documents page.
Preconcentration of methane (CH4) from air is a critical sampling step in the measurement of singly and doubly substituted isotopologue ratios. We demonstrate the potential for isotope fractionation during preconcentration onto and elution from the common trapping material HayeSep-D and investigate its significance in laser spectroscopy measurements. By altering the trapping temperature for adsorption, the flow direction of CH4 through the trap and the time at which CH4 is eluted during a desorption temperature ramp, we explain the mechanisms behind fractionation affecting δ13C(CH4) and δ2H(CH4). The results highlight that carbon isotope fractionation is driven by advection and diffusion, while hydrogen isotope fractionation is driven by the interaction of CH4 with the adsorbing material (tending to smaller isotopic effects at higher temperatures). We have compared the difference between the measured isotope ratio of sample gases (compressed whole air and a synthetic mixture of CH4 at ambient amount fraction in an N2 matrix) and their known isotopic composition. An open-system Rayleigh model is used to quantify the magnitude of isotopic fractionation affecting measured δ13C(CH4) and δ2H(CH4), which can be used to calculate the possible magnitude of isotopic fractionation given the recovery percentage. These results provide a quantitative understanding of isotopic fractionation during the sample preparation of CH4 from ambient air. The results also provide valuable insights applicable to other cryogenic preconcentration systems, such as those for measurements that probe the distribution of rarer isotopologues.
IsoMET at the Observations within the Global Greenhouse Gas Watch01.11.23
Bibhasvata Dasgupta (right) of project partner Universiteit Utrecht recently provided a poster presentation. The Use of Methane Isotope Measurements to Constrain Regional Scale Emissions was presented at the Observations within the Global Greenhouse Gas Watch, 3rd – 5th October in Geneva.
The purpose of this WMO workshop was to develop guidance from and to Member countries and partner organizations regarding the comprehensive integrated observing system that would support the implementation of the Global Greenhouse Gas Watch (GGGW).
01.07.23
A successful M9 meeting for the isoMET project was held by project partner PTB in June.
Javis Nwaboh (PTB) coordinator of the project welcomed all to the meeting. This was followed by presentations on work progressed under WP1 (Developing a harmonised in situ CH4 isotope dataset of ambient air in Europe) by Javis Nwaboh and Jelka Braden-Behrens (PTB) and associated partners NPL, TUBITAK, Empa, UU, The University of Glasgow, VTT, Royal Holloway and Bedford New College, UHEI, Université De Versailles Saint-Quentin-En-Yvelines and Stockholms Universitet.
Presentations on work progressed under WP2 (A sustainable metrological infrastructure for a dataset for CH4 isotope source signature measurements in Europe) were provided by Joachim Mohn, (Empa) and associated partners NPL, TUBITAK, PTB, Universiteit Utrecht, The University of Glasgow, VTT, Royal Holloway and Bedford New College, Ruprecht-Karls-Universitaet Heidelberg, Université De Versailles Saint-Quentin-En-Yvelines and The University of Bristol.
For WP3 (Atmospheric transport modelling to direct the measurement strategy for optimal emissions estimation and demonstration of emissions estimates from new datasets) progress was presented to the consortium by Tim Arnold (NPL) and associated partners The University of Bristol and Empa.
Presentations on work progressed under WP4 (Creating impact) were provided by Mehr Fatima and Thomas Hausmaninger (VTT). Javis Nwaboh (PTB) and Tim Arnold, (NPL) provided updates on WP5 (Management and coordination). During the work package presentations and discussions, there was further discussion with the consortium regarding the output of the project and future progress towards M18.
20.06.23
The isoMET project partners held a Stakeholder Workshop online on the 13th June 2023. Javis Nwaboh (PTB) coordinator of the project welcomed all to the meeting. This was followed by A presentation on WP1 (Developing a harmonised in situ CH4 isotope dataset of ambient air in Europe) by PTB. A presentation on work progressed under WP2 (A sustainable metrological infrastructure for a dataset for CH4 isotope source signature measurements in Europe) was provided by Empa. WP3 (Atmospheric transport modelling to direct the measurement strategy for optimal emissions estimation and demonstration of emissions estimates from new datasets) progress was presented by NPL. VTT presented on WP4 (Creating Impact).
During the work package presentations and discussions, there was further discussion between the consortium and the stakeholders regarding the output of the project, further stakeholder engagement and future progress towards M18.
01.03.23
The isoMET project partners will come together to discuss current progress and work towards M18 at PTB in Braunschweig, Germany, June 2023.
23.11.22
A successful Kick Off meeting for the isoMET Project was held by PTB on the 22nd November. Due to the current pandemic situation, the meeting was held online with all project partners in attendance.
Javis Nwaboh and Volker Ebert of PTB welcomed all the partners to the first meeting of this new project. Tim Arnold (NPL) provided an overview of the project overall, and Javis and Anas Emad (PTB) provided a summary of what is required under WP1.
Joachim Mohn (EMPA) took the partners through an overview of WP2, and Tim presented on WP3. Mehr Fatima and Thomas Hausmaninger (VTT) provided an overview of WP4.
EURAMET provided the presentation Guidance on the Metrology Partnership’s impact generation and reporting to the partners, and this was followed by Javis, Volker and Tim providing everyone with an overview for all partners requirements towards WP5.
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