Carbon Cycle GroupICOSResearch TopicsPeople & ContactDataPublications

Carbon Cycle Group

Measuring station on the roof of the IUP

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

Delta14CO2 in the global atmosphere from 1950 until 2019

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.

Download 14C Data

Read more:
→ Levin et al., 2010
→ Levin & Hesshaimer, 2000

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 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


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


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


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


All Publications

Recent Publications:


  • 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],, 2024.

  • 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,


  • 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,, 2023.

  • Karstens, U. and Levin, I.: Update and evaluation of a process-based radon flux map for Europe (V1.0). ICOS RI,, 2023.

  • 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,, 2023.

  • 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],, 2023.

  • 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,

  • 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],, 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],, 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,, 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.
  • 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:, 2023.


  • Levin, I. and Hammer, S.: Supplementary data to Levin et al. (2022), Continuous measurements of 14C in atmospheric CO2 at Cape Grim, 1987-2016., 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.
  • 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,, 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:, 2022.



  • 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,, 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,, 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.