Carbon Cycle Group
The carbon cycle group at IUP investigates the biogeochemical cycles of long-lived greenhouse gases such as CO2, CH4 N2O and SF6 on the regional but also on the global scale. We measure their long-term atmospheric trends and for CO2 also the radiocarbon (14C) content. Further, atmospheric 222Radon activity concentration measurements are conducted as we use this natural radioactive noble gas as tracer to evaluate atmospheric transport processes. In collaboration with the Max Planck Institute for Biogeochemistry in Jena these data are evaluated based on regional and global atmospheric transport models.
In the last decade, the IUP carbon cycle group contributed to the design and implementation of the European Research Infrastructure ICOS (Integrated Carbon Observation System) and has set up in Heidelberg the Central Radiocarbon Laboratory (CRL) as part of the Central Analytical Laboratory of ICOS.
Read more: The Integrated Carbon Observation System in Europe
Karl Otto Münnich Radiocarbon Laboratory of ICOS (ICOS CRL)
The ICOS CRL builds upon the former Heidelberg Radiocarbon Laboratory, which was operated for more than 50 years by IUP and the Heidelberg Academy of Sciences. The main task of the ICOS CRL is high precision radiocarbon analysis of CO2 samples from the ICOS atmospheric station network. These 14C measurements are used to separate the fossil fuel from the biogenic source contributions in atmospheric CO2 over Europe. The ICOS CRL was named after the first director of IUP, Karl Otto Münnich. During his PhD in the 1950s he has set up the Heidelberg Radiocarbon Laboratory.
Research Topics
Long-term monitoring of 14CO2 in the global atmosphere
Radiocarbon (14C) is the natural radioactive carbon isotope, which is produced in the atmosphere by cosmic ray-induced reactions with atmospheric nitrogen. The radioactive half life of 14C is 5700 years. In an undisturbed steady state situation the atmospheric 14CO2 activity corresponds to an equilibrium between its production in the atmosphere and its radioactive decay in all carbon reservoirs exchanging CO2 with the atmosphere. The natural equilibrium level of atmospheric 14CO2 (reference level) has been disturbed through man's activities in the last century, by the ongoing input of fossil fuel CO2 into the atmosphere known as Suess effect, and through nuclear bomb testing in the atmosphere in the 1950s and early 1960s (14C bomb effect). After the atmospheric test ban treaty in 1963, 14CO2 reached its maximum in the Northern Hemisphere. The subsequent decrease is due to carbon exchange between atmosphere, ocean and biosphere. Today the decrease is mainly due to the ongoing input of 14C-free fossil fuel CO2 into the global atmosphere.
Long-term monitoring of 14CO2 in the regional atmosphere
Carbon dioxide (CO2) released from burning of fossil fuels is void of radiocarbon. At a polluted station close to fossil fuel emissions, the atmospheric 14C/C ratio in CO2 is thus diluted by 14C-free fossil CO2 emissions. By comparing the 14C/C ratio at a polluted station, such as the ICOS pilot station Heidelberg, to that in clean air, e.g. Jungfraujoch, we can estimate the locally added fossil fuel CO2 concentration at the polluted station (red histogram). Note that in Heidelberg about half of the local CO2 concentration offset compared to background air is of biogenic origin (green histogram).
Read more:
→ Levin & Hammer 2018
→ Levin et al., 2011
→ Levin & Rödenbeck, 2008
ICOS Cities (PAUL)
'Pilot Application in Urban Landscapes - Towards integrated city observatories for greenhouse gases' is a 4-year H2020 project to support the EUROPEAN GREEN DEAL by creating capabilities to observe and verify greenhouse gas emissions from densely populated urban areas across Europe.
Our Contribution: Feasibility studies and implementation of 14CO2 analyses on relaxed eddy accumulation samples. Conducting the 14CO2 measurements for the urban observations in Paris
VERIFY
VERIFY develops a system to estimate greenhouse gas emissions to support countries' emission reporting to the UN Climate Change Convention Secretariat. The emissions are estimated based on land, ocean and atmospheric observations.
Our Contribution: Testing of surrogate tracers (CO, NOx) for fossil fuel CO2
traceRadon
Radon metrology for use in climate change observation and radiation protection at the environmental level
Our Contribution as Collaborators: Intercomparison of the Heidelberg Radon Monitor with other atmospheric radon monitors, improvement of a radon soil flux map for Europe
Read more:
→ Strahlenschutzpraxis 2/2021, in German
→ Röttger et al 2021
ATTO
Amazon Tall Tower Observatory - contributions to carbon cycle and climate research
Our Contributions: 14CO2 and 222Rn measurements, development of a radon soil flux map for Brazil
CORSO
CO2MVS Research on Supplementary Observations
CORSO will support establishing the new CO2MVS (CO2 Monitoring and Verification System) by delivering the capabilities at global and local scale to optimally use observations of co-emitted species using their emission ratios and uncertainties to better estimate anthropogenic CO2 emissions. It will also assess the added-value of high-temporal resolution 14CO2 and in-situ APO observations in global and regional scale inversions to better separate the impact of fossil fuel and biospheric fluxes on the atmospheric CO2 concentrations.
Our Contributions: Analyse each flask sample collected in 2024 at 11 selected ICOS class-1 stations as well as at the station Bialystok in Poland. Compile and intercompare 14CO2 data from globally distributed background stations
People & Contacts
Bachelor, Master and PhD students are welcome to contact Samuel Hammer if interested in thesis topics
| Name | Group | Position | Room | Tel.: +49-6221- |
| Julian Della Coletta | ICOS | Technician | Mathematikon / L118 | 54 6376 |
| Maksym Gachkivskyi | ICOS | PhD Student | INF 229/ R334 | 54 6354 |
| Zoe Madeleine Schwalbe | ICOS | Technician | Mathematikon / L133 | 54 6333 |
| Samuel Hammer | ICOS | Group Leader | Mathematikon / L116 | 54 6357 |
| Hannes Juchem | ICOS | Master Student | Mathematikon / L118 | 54 6376 |
| Caterina Keller | ICOS | Secretary | Mathematikon / L119 | 54 6377 |
| Timo Knaack | ICOS | Master Student | Mathematikon / L119 | 54 6377 |
| Ann-Kristin Kunz | ICOS | PhD Student | Mathematikon / L118 | 54 6376 |
| Sabine Kühr | ICOS | Technician | Mathematikon / L133 | 54 6333 |
| Ingeborg Levin | Carbon Cycle | Retiree | INF 229 / R318 | 54 6330 |
| Jan-Philip Ott | ICOS | Student Helper | ||
| Susanne Preunkert | ICOS | Research Scientist | Mathematikon / L114 | 54 6359 |
| Stefan Sapper | ICOS | Technician | Mathematikon / L133 | 54 6333 |
Data sets from earlier research projects
- SF6 records from Neumayer Station (Antarctica), Cape Grim (Tasmania/Australia), Izaña (Tenerife/Spain), Fraserdale (Canada), Alert (Canada) and meridional profiles (Atlantic Ocean) (Maiss et al., 1996).
download data - FTIR data from Heidelberg 2011-2015
download data - δ13C(CH4) records of clean air monitoring stations at Alert (Ellesmere Island, Nunavut, Canada), Izaña (Tenerife/Spain), and Neumayer Station (Dronning Maud Land, Antarctica) (Levin et al., 2012).
download data (Alert)
download data (Izaña)
download data (Neumayer)
view graph.pdf (data + harmonic fits)
Publications
Recent Publications:
2024
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Machado, L. A. T., Kesselmeier, J., Botia, S., Van Asperen, H., de Araújo, A. C., Artaxo, P., Edtbauer, A., Ferreira, R., Harder, H., Jones, S., Dias-Júnior, C. Q., Haytzmann, G. G., Quesada, C. A., Komiya, S., Lavric, J., Lelieveld, J., Levin, I., Nölscher, A., Pfannerstill, E., Pöhlker, M., Pöschl, U., Ringsdorf, A., Rizzo, L., Yáñez-Serrano, A. M., Trumbore, S., Valenti, W. I. D., Vila-Guerau de Arellano, J., Walter, D., Williams, J., Wolff, S., and Pöhlker, C.: How Rainfall Events Modify Trace Gas Concentrations in Central Amazonia, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-2901, 2024.
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Papale, D., and Coauthors, 2024: Standards and Open Access are the ICOS Pillars: Reply to “Comments on ‘The Integrated Carbon Observation System in Europe’”, Bull. Amer. Meteor. Soc., 104, 953–955, https://doi.org/10.1175/BAMS-D-23-0216.1.
2023
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Zazzeri, G., Graven, H., Xu, X., Saboya, E., Blyth, L., Manning, A.J., Chawner, H., Wu, D. and Hammer, S.: Radiocarbon measurements reveal underestimated fossil CH4 and CO2 emissions in London. Geophysical Research Lett. 50, https://doi.org/10.1029/2023GL103834, 2023.
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Karstens, U. and Levin, I.: Update and evaluation of a process-based radon flux map for Europe (V1.0). ICOS RI, https://hdL.handle.net/11676/8PqEdm7ARD6aPepClmktPm2K, 2023.
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Rödenbeck, C., Adcock, K. E., Eritt, M., Gachkivsky, M., Gerbig, C., Hammer, S., Jordan, A., Keeling, R. F., Levin, I., Maier, F., Manning, A. C., Moossen, H., Munassar, S., Pickers, P. A., Rothe, M., Tohjima, Y., and Zaehle, S.: The suitability of atmospheric oxygen measurements to constrain Western European fossil-fuel CO2 emissions and their trends, Atmos.Chem.Phys., 23, 15767-15782, https://doi.org/10.5194/acp-23-15767-2023, 2023.
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Steiner, M., Peters, W., Luijkx, I., Henne, S., Chen, H., Hammer, S., and Brunner, D.: European CH4 inversions with ICON-ART coupled to CarbonTracker Data Assimilation Shell, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-853, 2023.
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Hammer, S., Levin, I., Atmosphere Thematic Centre, ICOS-CAL-FCL (2023). Atmospheric CH4 product, Heidelberg (30.0 m), 1996-01-01–2023-03-31, European ObsPack, https://hdl.handle.net/11676/iHEvIV3yodKr7xb0fvQXxUrf.
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Maier, F. M., Rödenbeck, C., Levin, I., Gerbig, C., Gachkivskyi, M., and Hammer, S.: Potential of 14C-based versus ∆CO-based ∆ffCO2 observations to estimate urban fossil fuel CO2 (ffCO2) emissions, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-1239, 2023, accepted.
- Maier, F. M., Levin, I., Conil, S., Gachkivskyi, M., Denier van der Gon, H., and Hammer, S.: Uncertainty of continuous ∆CO-based ∆ffCO2 estimates derived from 14C flask and bottom-up ∆CO / ∆ffCO2 ratios, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-1237, 2023.
- Worthy, D. E. J., Rauh, M. K., Huang, L., Vogel, F. R., Chivulescu, A., Masarie, K. A., Langenfelds, R. L., Krummel, P. B., Allison, C. E., Crotwell, A. M., Madronich, M., Pétron, G., Levin, I., Hammer, S., Michel, S., Ramonet, M., Schmidt, M., Jordan, A., Moossen, H., Rothe, M., Keeling, R., and Morgan, E. J.: Results of a Long-Term International Comparison of Greenhouse Gas and Isotope Measurements at the Global Atmosphere Watch (GAW) Observatory in Alert, Nunavut, Canada, Atmos. Meas. Tech., 16, 5909–5935, https://doi.org/10.5194/amt-16-5909-2023, 2023.
- Maier, F., Levin, I., Gachkivskyi, M., Rödenbeck, C. and Hammer, S.: Estimating regional fossil-fuel CO2 concentrations from 14CO2 observations: Challenges and uncertainties. Phil. Trans. R. Soc. A 381:20220203.
https://doi.org/10.1098/rsta.2022.0203 - Ramonet, M., Chatterjee, A., Ciais, P., Levin, I., Sha, M., Steinbacher, M., and Sweeney, C.: CO2 in the atmosphere: growth and trends since 1850. In Oxford Research Encyclopedia of Oxford Research Encyclopedia of Climate Science. Oxford University Press. doi: https://doi.org/10.1093/acrefore/9780190228620.013.863, 2023.
2022
- Levin, I. and Hammer, S.: Supplementary data to Levin et al. (2022), Continuous measurements of 14C in atmospheric CO2 at Cape Grim, 1987-2016. https://doi.org/10.18160/8F31-EQDJ, 2022.
- Apadula, F., Arnold, S., Bergamaschi, P., Biermann, T., Blanc, P.-E., Brunner, D., Chen, H., Chmura, L., Colomb, A., Conil, S., Couret, C., Cristofanelli, P., De Mazière, M., Delmotte, M., Emmenegger, L., Forster, G., Frumau, A., Gerbig, C., Gheusi, F., Hammer, S., Haszpra, L., Hatakka, J., Heliasz, M., Heltai, D., Henne, S., Hensen, A., Hermansen, O., Hoheisel, A., Kneuer, T., Komínková, K., Kubistin, D., Laurent, O., Laurila, T., Lehner, I., Lehtinen, K., Leskinen, A., Leuenberger, M., Levin, I., Levula, J., Lindauer, M., Lopez, M., Lund Myhre, C., Lunder, C., Mammarella, I., Manca, G., Manning, A., Marek, M., Marklund, P., Martin, D., Meinhardt, F., Mölder, M., Müller-Williams, J., Narbaud, C., Necki, J., O'Doherty, S., Ottosson-Löfvenius, M., Philippon, C., Piacentino, S., Pichon, J.-M., Pitt, J., Platt, S.M., Plaß-Dülmer, C., Ramonet, M., Rivas-Soriano, P., Scheeren, B., Schmidt, M., Schumacher, M., Sha, M.K., Smith, P., Spain, G., Steinbacher, M., Sørensen, L.L., Trisolino, P., Vermeulen, A., Vítková, G., Xueref-Remy, I., Yver-Kwok, C., di Sarra, A., ICOS Atmosphere Thematic Centre, ICOS Flask And Calibration Laboratory (FCL), ICOS Central Radiocarbon Laboratory (CRL), ICOS ERIC, 2022. European atmospheric CO2 and CH4 Mole Fraction data product - 2022. https://doi.org/10.18160/1RE0-2GKH
- Maier, F., Gerbig, C., Levin, I., Super, I., Marshall, J., and Hammer, S.: Effects of point source emission heights in WRF–STILT: a step towards exploiting nocturnal observations in models, Geosci. Model Dev., 15, 5391–5406, https://doi.org/10.5194/gmd-15-5391-2022, 2022.
- Levin, I., Hammer, S., Kromer, B., Preunkert, S., Weller, R., and Worthy, D.E.: Radiocarbon in tropospheric carbon dioxide, Radiocarbon, Vol 64, Nr 4, 2022, p 781–791. DOI: https://doi.org/10.1017/RDC.2021.102, 2022.
2021
- Levin, I, Hammer S.: Supplementary data to Levin et al. (2021), Radiocarbon in global tropospheric carbon dioxide, ICOS-ERIC Carbon Portal, doi:10.18160/K6P6-WBH5, 2021.
- Hua, Q., Turnbull, J.C., Santos, G.M., Rakowski, A.Z., Ancapuchún, De Pol Holz, R., Hammer, S., Lehmann, S.J., Levin, I., Miller, J.B., Palmer, J.G. and Turney, C.S.M.: Atmospheric radiocarbon for the period of 1950 - 2019, Radiocarbon, 1-23. doi:10.1017/RDC.2021.95, 2021.
- Heiskanen, J., Brümmer, C., Buchmann, N., Calfapietra, C., Chen, H., Gielen, B., Gkritzalis, T., Hammer, S., Hartman, S., Herbst, M., Janssens, I. A., Jordan, A., Juurola, E., Karstens, U., Kasurinen, V., Kruijt, B., Lankreijer, H., Levin, I., Linderson, M.-L., Loustau, D., Merbold, L., Lund Myhre, K., Papale, D., Pavelka, M., Pilegaard, K., Ramonet, M., Rebmann, C., Rinne, J., Rivier, L., Saltikoff, E., Sanders, R., Steinbacher, M., Steinhoff, T., Watson, A., Vermeulen, A. T., Vesala, T., Vítková, G., and Kutsch, W.: The Integrated Carbon Observation System in Europe, Bulletin of the American Meteorological Society.; https://doi.org/10.1175/BAMS-D-19-0364, 2021.
- Levin, I., Karstens, U., Hammer, S., DellaColetta, J., Maier, F., and Gachkivskyi, M.: Limitations of the Radon Tracer Method (RTM) to estimate regional Greenhouse Gases (GHG) emissions – a case study for methane in Heidelberg, Atmos. Chem. Phys., 21, 17907–17926, https://doi.org/10.5194/acp-21-17907-2021, 2021.
- Levin, I. and Hammer, S.: Supplementary data to Levin et al. (2021), Limitations of the Radon Tracer Method (RTM) to estimate regional Greenhouse Gases (GHG) emissions – a case study for methane in Heidelberg, ICOS-ERIC Carbon Portal [data set], https://doi.org/10.18160/WGS0-F7DY, 2021.
- Levin, I. and Cuntz, M.:. Measurement of stable isotopes in carbon dioxide, methane, and water vapor. In: Foken T. (ed), Handbook of Atmospheric Measurements. Springer Nature, Cham, Switzerland, 509-532. https://doi.org/10.1007/978-3-030-52171-4_17, 2021.
- Kromer, B., Levin, I., Lindauer, S., Jähne, B., Münnich, M., Platt, U. and Schlosser, P.: Karl Otto Münnich (1925-2003): In Memoriam, Radiocarbon, https://www.doi.org/10.1017/RDC.2021.38, 2021.
2020
- Levin, I., Karstens, U., Eritt, M., Maier, F., Arnold, S., Rzesanke, D., Hammer, S., Ramonet, M., Vítková, G., Conil, S., Heliasz, M., Kubistin, D., and Lindauer, M.: A dedicated flask sampling strategy developed for ICOS stations based on CO2 and CO measurements and STILT footprint modelling, Atmos. Chem. Phys., 11161-11180, https://doi.org/10.5194/acp-20-11161-2020, 2020.
- Ramonet, M., P. Ciais, F. Apadula, J. Bartyzel , A. Bastos, P. Bergamaschi, P. E. Blanc, D. Brunner, L. C. d. Torchiaro, F. Calzolari, H. Chen, L. Chmura, A. Colomb, S. Conil, P. Cristofanelli, E. Cuevas, R. Curcoll, M. Delmotte, A. d. Sarra, L. Emmenegger, G. Forster, A. Frumau, C. Gerbig, F. Gheusi, S. Hammer, L. Haszpra, J. Hatakka, L. Hazan, M. Heliasz, S. Henne, A. Hensen, O. Hermansen, P. Keronen, R. Kivi, K. Kominkova, D. Kubistin, O. Laurent, T. Laurila, J. Lavric, I. Lehner, K.E.J. Lehtinen, A. Leskinen, M. Leuenberger, I. Levin, M. Lindauer, M. Lopez, C. L. Myhre, I. Mammarella, G. Manca, A. Manning, M. V. Marek, P. Marklund, D. Martin, F. Meinhardt, N. Mihalopoulos, M. Molder, J. A. Morgui, J. Necki, S. O'Doherty, C. O'Dowd, M. Ottosson, C. Philippon, S. Piacentino, J. M. Pichon, C. Plass-Duelmer, A. Resovsky, L.Rivier, X. Rodó, M.K. Sha, H. Scheeren, D. Sferlazzo, T. G. Spain, K. M. Stanley, M. Steinbacher, P. Trisolano, A. Vermeulen, G. Vítková, D. Weyrauch, I. Xueref-Remy, K. Yala and C. Yver Kwok,: The fingerprint of the summer 2018 drought in Europe on ground-based atmospheric CO2 measurements. Philos. T. R. Soc. B 375: 20190513, 2020, https://dx.doi.org/10.1098/rstb.2019.0513, 2020.
- Grossi, C., Chambers, S. D., Llido, O., Vogel, F. R., Kazan, V., Capuana, A., Werczynski, S., Curcoll, R., Delmotte, M., Vargas, A., Morguí, J.-A., Levin, I., and Ramonet, M.: Inter-comparison study of atmospheric 222Rn and 222Rn progeny monitors. Atmos. Meas. Tech., 13, 2241–2255, https://doi:10.5194/amt-13-2241-2020, 2020.
2019
- Nisbet, E. G., Manning, M. R., Dlugokencky, E. J., Fisher, R. E., Lowry, D., Michel, S. E., C. Lund Myhre, C., Platt, S.M., Allen, G., Bousquet, P., Brownlow, R., Cain, M., France, J.L., Hermansen, O., Hossaini1, R., Jones, A.E., Levin, I., Manning, A.C., Myhre, G., Pyle, J.A., Vaughn, B.H., Warwick, N.J., and White, J.W.C.: Very strong atmospheric methane growth in the 4 years 2014–2017: Implications for the Paris Agreement. Global Biogeochemical Cycles, 33; https://doi:10.1029/2018GB006009, 2019.
2018
- Bergamaschi, P., Karstens, U., Manning, A., Saunois, M., Tsuruta, A., Berchet, A., Vermeulen, A., Arnold, T., Janssens-Maenhout, G., Hammer, S., Levin, I., Schmidt, M., Ramonet, M., Lopez, M., Lavric, J., Aalto, T., Chen, H., Feist, D.G., Gerbig, C., Haszpra, L., Hermansen, O., Manca, G., Moncrieff, J., Meinhardt, F., Necki, J., Galkowski, M., O'Doherty, S., Paramonova, N., Scheeren, H., Steinbacher, M., and Dlugokencky, E.: Inverse modelling of European CH4 emissions during 2006-2012 using different inverse models and reassessed atmospheric observations, Atmos. Chem. Phys., https://doi:10.5194/acp-18-901-2018, 2018.
- Umezawa, T., Brenninkmeijer, C. A. M., Röckmann, T., van der Veen, C., Tyler, S. C., Fujita, R., Morimoto, S., Aoki, S., Sowers, T., Schmitt, J., Bock, M., Beck, J., Fischer, H., Michel, S. E., Vaughn, B. H., Miller, J. B., White, J. W. C., Brailsford, G., Schaefer, H., Sperlich, P., Brand, W. A., Rothe, M., Blunier, T., Lowry, D., Fisher, R. E., Nisbet, E. G., Rice, A. L., Bergamaschi, P., Veidt, C., and Levin, I.: Interlaboratory comparisons of δ13C and δD measurements of atmospheric CH4 for combined use of datasets from different laboratories. Atmos. Meas. Tech., 11, 1207–1231, https://doi:10.5194/amt-11-1207-2018, 2018.
- Kuderer, M., Hammer, S., and Levin, I.: The influence of 14CO2 releases from regional nuclear facilities at the Heidelberg 14CO2 sampling site (1986–2014). Atmos. Chem. Phys., 18, 7951–7959, https://doi:10.5194/acp-18-7951-2018, 2018.
- Griffith, D. W., Pohler, D., Schmitt, S., Hammer, S., Vardag, S., and Platt, U.: Long open-path measurements of greenhouse gases in air using near-infrared Fourier transform spectroscopy. Atmos. Meas. Tech., 11, 1549–1563, 2018.
- Major, I., Haszpra, L., Rinyu, L., Futó, I., Bihari, Á., Hammer, S., Jull, A.J.T., and Molnár, M.: Temporal Variation of Atmospheric Fossil and Modern CO 2 Excess at a Central European Rural Tower Station between 2008 and 2014. Radiocarbon, 60(5), 1285-1299, 2018.
- Palonen, V., Pumpanen, J., Kulmala, L., Levin, I., Heinonsalo, J. and Vesala, T.: Seasonal and diurnal variations in atmospheric and soil air 14CO2 in a boreal Scots Pine forest. Radiocarbon, 60(1), 283-297, https://doi:10.1017/rdc.2017.95, 2018.
2017
- Levin, I., Schmithüsen, D. and Vermeulen, A.: Assessment of 222Radon progeny loss in long tubing based on static filter measurements in the laboratory and in the field. Atmos. Atmos. Meas. Tech., 10, 1313–1321, doi:10.5194/amt-10-1313-2017, 2017.
- Prokopiou, M., P. Martinerie, C. J. Sapart, E. Witrant, G. A. Monteil, K. Ishijima, S. Bernard, J. Kaiser, I. Levin, T. Sowers, T. Blunier, D. Etheridge, E. Dlugokencky, R. S. W. van de Wal, and T. Röckmann: Constraining N2O emissions since 1940 using firn air isotope measurements in both hemispheres. Atmos. Chem. Phys., 17, 4539–4564, doi:10.5194/acp-17-4539-2017, 2017.
- Orr, J. C., Najjar, R.G., Aumont, O., Bopp, L., Bullister, J.C., Danabasoglu, D, Doney, S.C., Dunne, J.P., Dutay, J.-C., Graven, H., Griffies, S.M., John, J.G., Joos, F., Levin, I., Lindsay, K., Matear, R.J., McKinley, G.A., Mouchet, A., Oschlies, A., Romanou, A., Schlitzer, R., Tagliabue, A., Tanhua, T. and Yool, A.: OMIP biogeochemical protocols and diagnostics for CMIP6. Geoscientific Model Development, 10, 2169-2199, 2017, doi:10.5194/gmd-10-2169-2017, 2017.
- Schmithüsen, D., Chambers, S., Fischer, B., Gilge, S., Hatakka, J., Kazan, V., Neubert, R., Paatero, J., Ramonet, M., Schlosser, C., Schmid, S., Vermeulen, A. and Levin, I.: A European-wide 222Radon and 222Radon progeny comparison study. Atm. Meas. Tech., 10, 1299–1312, 2017, doi:10.5194/amt-10-1299-2017, 2017.
- Schmithüsen, D., Chambers, S., Fischer, B., Gilge, S., Hatakka, J., Kazan, V., Neubert, R., Paatero, J., Ramonet, M., Schlosser, C., Schmid, S., Vermeulen, A., and Levin, I.: A European - wide 222Radon and 222Radon progeny comparison study [Dataset], 2017, https://doi:10.1158/data/10098, 2017.
- Hammer, S. and Levin, I.: Monthly mean atmospheric Δ12CO2 at Jungfraujoch and Schauinsland from 1986 to 2016 [Dataset], https://doi:10.11588/data/10100, 2017.
- Graven, H., Allison, C. E., Etheridge, D. M., Hammer, S., Keeling, R. F., Levin, I., Meijer, H. A. J., Rubino, M., Tans, P. P., Trudinger, C. M., Vaughn, B. H. and White, J. W. C.: Compiled records of carbon isotopes in atmospheric CO2 for historical simulations in CMIP6. Geoscientific Model Development, 10, No 12, 4405-4417. https://doi:10.5194,/gmd-10-4405-2017, 2017.
- Berhanu, T. A., Szidat, S., Brunner, D., Satar, E., Schanda, R., Nyfeler, P., Battaglia, M., Steinbacher, M., Hammer, S., Leuenberger, M.: Estimation of the fossil fuel component in atmospheric CO2 based on radiocarbon measurements at the Beromünster tall tower, Switzerland. Atmos. Chem. Phys. 17, 10753-10766, https://doi:10.5194/acp-17-10753-2017, 2017.
- Hammer, S., Friedrich, R., Kromer, B., Cherkinsky, A., Lehman, S. J., Meijer, H. A., Nakamura, T., Palonen, V., Reimer, R.W,, Smith, A.M., Southon, J.R., Szidat, S., Turnbull, J., and Uchida; M.: Compatibility of atmospheric 14CO2 measurements: Comparing the Heidelberg low-level counting facility to international accelerator mass spectrometry (AMS) laboratories. Radiocarbon, 59(3), 875-883, https://doi:10.1017/RDC.2016.62, 2017.