Whole air samples to determine long-term concentration trends of greenhouse gases and their isotopic composition are taken by the IUP-Heidelberg (PI: Ingeborg Levin). The long-term increase of CO2, caused by an ongoing input of CO2 from fossil fuel burning and land-use change into the atmosphere, was almost linear over the last decade (growth rate 1.8 ppm 1/yr), however, large inter-annual variations are obvious. For example in 1997/98 during a strong El Niño period a positive CO2 anomaly was observed which is accompanied by a significant decrease of delta 13C-CO2, indicating unusually large continental biogenic CO2 emissions during this period.
14CO2 samples were collected atNeumayer since 1983. The long-term Δ14C decrease observed is mainly caused by oceanic uptake of bomb 14CO2 and by the ongoing in put of 14C-free fossil fuel CO2 into the atmosphere. The Neumayer Δ14CO2 level was slightly lower than that at Jungfraujoch (47°N) in the early years, due to the strong 14CO2 disequilibrium flux between the atmosphere and circum-Antarctic surface ocean water. However, in the last five years the north-south difference has changed sign as 14C-free fossil fuel CO2 emissions are steadily increasing in particular in the northern hemisphere.
Levin, I., T. Naegler, B. Kromer, M. Diehl, R.J. Francey, A.J. Gomez‑Pelaez, L.P. Steele, D. Wagenbach, R. Weller, and D.E. Worthy, Observations and modelling of the global distribution and long‑term trend of atmospheric 14CO2, TellusB(1), 62, pp. 26‑46. doi: 10.1111/j.1600‑0889.2009.00446.x, 2010.
Ingeborg Levin, Samuel Hammer, Bernd Kromer, Susanne Preunkert, Rolf Weller, Douglas E Worthy. Radiocarbon in global tropospheric carbon dioxide, Radiocarbon, DOI:10.1017/RDC.2021.102.