Research Themes

Paleoclimate Reconstruction

Paleoclimate research is a major focus of my work, in which I apply both novel and classical isotope proxies to quantify Earth’s past climate variability and environmental change. My research spans from the Precambrian through the Mesozoic to the Cenozoic and includes both marine and terrestrial archives. By quantifying past climate states and perturbations, this work provides a long-term perspective on climate sensitivity and helps place modern anthropogenic climate change into a geological context.

  • Price, G.D., Bajnai, D. & Fiebig, J., 2020. Carbonate clumped isotope evidence for latitudinal seawater temperature gradients and the oxygen isotope composition of Early Cretaceous seas. Palaeogeography, Palaeoclimatology, Palaeoecology, 552, 109777. https://doi.org/10.1016/j.palaeo.2020.109777
  • Page, M., Licht, A., Dupont-Nivet, G., Meijer, N., Barbolini, N., Hoorn, C., Schauer, A., Huntington, K., Bajnai, D., Fiebig, J., Mulch, A. & Guo, Z. (2019) Synchronous cooling and decline in monsoonal rainfall in northeastern Tibet during the fall into the Oligocene icehouse. Geology, 47, (3), 203-206. https://doi.org/10.1130/g45480.1

Paleoclimate Proxy Developement

A key component of my work is the development and refinement of novel paleoclimate proxies, including carbonate dual clumped isotopes and triple oxygen isotopes. Beyond exploring their potential to advance quantitative paleoclimate reconstruction, I am actively engaged in interlaboratory standardization efforts to improve analytical consistency and comparability across research groups.

  • Bajnai, D., Guo, W., Spötl, C., Coplen, T.B., Methner, K., Löffler, N., Krsnik, E., Gischler, E., Hansen, M., Henkel, D., Price, G.D., Raddatz, J., Scholz, D. & Fiebig, J. (2020) Dual clumped isotope thermometry resolves kinetic biases in carbonate formation temperatures. Nature Communications, 11, 4005. https://doi.org/10.1038/s41467-020-17501-0
  • Bajnai, D., Klipsch, S., Davies, A. J., Raddatz, J., Gischler, E., Rüggeberg, A., Pack, A. & Herwartz, D. (2024). Correcting for vital effects in coral carbonate using triple oxygen isotopes. Geochemical Perspectives Letters, 31, 38–43. https://doi.org/10.7185/geochemlet.2430

Biomineralization

I study the processes by which marine organisms, such as brachiopods and corals, precipitate their carbonate skeletons. This research provides mechanistic insights into how biominerals are formed and improves our understanding of how biological processes influence geochemical proxy signals.

  • Bajnai, D., Fiebig, J., Tomašových, A., Milner Garcia, S., Rollion-Bard, C., Raddatz, J., Löffler, N., Primo-Ramos, C. & Brand, U. (2018) Assessing kinetic fractionation in brachiopod calcite using clumped isotopes. Scientific Reports, 8, (1), 1-12. https://doi.org/10.1038/s41598-017-17353-7
  • Davies, A. J., Brand, U., Tagliavento, M., Bitner, M. A., Bajnai, D., Staudigel, P., Bernecker, M., and Fiebig, J. (2023). Isotopic disequilibrium in brachiopods disentangled with dual clumped isotope thermometry. Geochimica et Cosmochimica Acta, S0016703723003952. https://doi.org/10.1016/j.gca.2023.08.005
  • Bajnai, D., Klipsch, S., Davies, A. J., Raddatz, J., Gischler, E., Rüggeberg, A., Pack, A. & Herwartz, D. (2024). Correcting for vital effects in coral carbonate using triple oxygen isotopes. Geochemical Perspectives Letters, 31, 38–43. https://doi.org/10.7185/geochemlet.2430

Cyclostratigraphy

I apply cyclostratigraphic methods to resolve orbital-scale climate variability in sedimentary records, refining stratigraphic frameworks and quantifying high-resolution climate dynamics linked to astronomical forcing and Earth system feedbacks.

  • Bajnai, D., Pálfy, J., Martinez, M., Price, G.D., Nyerges, A. & Főzy, I. (2017) Multi-proxy record of orbital-scale changes in climate and sedimentation during the Weissert Event in the Valanginian Bersek Marl Formation (Gerecse Mts., Hungary). Cretaceous Research, 75, 45-60. https://doi.org/10.1016/j.cretres.2017.02.021
  • Müller, T., Price, G.D., Bajnai, D., Nyerges, A., Kesjár, D., Raucsik, B., Varga, A., Judik, K., Fekete, J., May, Z. & Pálfy, J. (2016) New multiproxy record of the Jenkyns Event (also known as the Toarcian Oceanic Anoxic Event) from the Mecsek Mountains (Hungary): Differences, duration and drivers. Sedimentology, 64, (1), 66-86. https://doi.org/10.1111/sed.12332
  • Vallner, Z., Müller, T., Bajnai, D., Szives, O., Csicsek, L. Á., Héja, G., Heszler, B., Zajzon, N., & Pálfy, J. (2026). Integrated astrochronology, isotope and biostratigraphy of the Albian-Cenomanian transition and expression of the OAE 1d in an expanded record of a rapidly subsiding Tethyan synorogenic basin (Core Jásd-42, Transdanubian Range, Hungary). Cretaceous Research, 181, 106311. https://doi.org/10.1016/j.cretres.2025.106311

Analytical Chemistry

I investigate isotope fractionation kinetics in aqueous systems, focusing on reactions involved in carbonate formation and thereby strengthening the foundation for accurate proxy-based climate reconstructions. I also love tinkering in the lab, improving the analytical techniques that underpin geochemical research.

  • Bajnai, D., Cao, X., Klipsch, S., Pack, A., & Herwartz, D. (2024). Triple oxygen isotope systematics of CO2 hydroxylation. Chemical Geology, 654, 122059. https://doi.org/10.1016/j.chemgeo.2024.122059
  • Bajnai, D., Pack, A., Arduin Rode, F., Seefeld, M., Surma, J., Di Rocco, T., 2023. A dual inlet system for laser spectroscopy of triple oxygen isotopes in carbonate-derived and air CO2. Geochemistry, Geophysics, Geosyststems, 24, e2023GC010976. https://doi.org/10.1029/2023GC010976

Atmospheric Chemistry

As a new avenue of research, I am analyzing triple oxygen isotopes in atmospheric CO2. These measurements have the potential to reveal changes in global primary productivity and to quantify the contributions from different natural and anthropogenic CO2 sources.

  • Bajnai, D., & Hare, V. J. (2025). Sensitivity of tunable infrared laser spectroscopic measurements of ∆’17O in CO2 to analytical conditions. Atmospheric Measurement Techniques, 18, 7405–7419. https://doi.org/10.5194/amt-18-7405-2025
  • Bajnai, D., Pack, A., Arduin Rode, F., Seefeld, M., Surma, J., & Di Rocco, T. (2023). A dual inlet system for laser spectroscopy of triple oxygen isotopes in carbonate-derived and air CO2. Geochemistry, Geophysics, Geosystems, 24, e2023GC010976. https://doi.org/10.1029/2023GC010976