27 November 2025 marks an important milestone for atmospheric research at the Jungfraujoch scientific station in the Bernese Alps. The Swiss Federal Office of Meteorology and Climatology (MeteoSwiss) and the University of Liège have inaugurated a new Fourier transform infrared (FTIR) spectrometer. This state-of-the-art instrument replaces one that has been in service for more than 30 years and ensures the continuation of one of the longest series of atmospheric observations in the world.
Since the early 1950s, the University of Liège (ULiège) has been observing the composition of the atmosphere from the Sphinx laboratory at Jungfraujoch, at an altitude of over 3,580 metres. At the time, Professor Marcel Migeotte installed an infrared spectrometer designed in Liège to take advantage of an exceptionally dry site, far from sources of pollution and accessible all year round by rail.
Between 1950 and 1951, his team systematically recorded the infrared solar spectrum and demonstrated the presence, in an atmosphere then considered ‘clean’, methane (CH₄), carbon monoxide (CO), nitrous oxide (N₂O), carbon dioxide (CO₂) and ozone (O₃). These pioneering observations still constitute a unique record of the state of the atmosphere before the era of major anthropogenic disturbances.
Relaunched in the mid-1970s, when the first concerns arose about the destruction of the ozone layer by chlorofluorocarbons (CFCs), the observation programme has continued uninterrupted ever since. Researchers in Liège are documenting the rapid accumulation of major greenhouse gases (CO₂, CH₄, N₂O), whose abundances have increased by 30 to 50% since the early 1950s, as well as the rise and then decline of stratospheric chlorine, which is responsible for the ozone hole.
Over the decades, the team has expanded its infrared ‘spectrographic library’ and developed analytical methods that now make it possible to regularly monitor more than 35 atmospheric constituents: greenhouse gases, ozone-related halogenated compounds, air pollutants, biomass combustion indicators, etc. These multi-decadal time series have become international benchmarks for the study of climate, air quality and atmospheric chemistry.
ULiège at the Jungfraujoch station
The FTIR instrument in service at Jungfraujoch was installed in the late 1980s. After more than 30 years of operation in a high-mountain environment, its reliability was declining and spare parts were becoming scarce, posing a real risk of interruption to the measurement series.
However, in order to detect subtle climate trends, such as the slow recovery of the ozone layer or the recent acceleration in methane increase, continuity and consistency of observations are essential. An uncontrolled ‘break’ in instrumentation can make it much more difficult, if not impossible, to interpret several decades of data.
It is precisely to avoid this scenario that MeteoSwiss has invested in the complete replacement of its FTIR instrumentation – spectrometer and celostat – between 2023 and 2025, as part of its contribution to the international reference programmes WMO Global Atmosphere Watch (GAW) and Global Climate Observing System (GCOS). The operation was carried out in close collaboration with ULiège, which provided and reinforced the scientific team to ensure the installation, commissioning, intercalibration and exploitation of the new system.
The new instrument, inaugurated on 27 November, offers very high spectral resolution across the entire infrared range operated at the Jungfraujoch. Coupled with a modernised control chain and increasingly automated operating procedures, it will enable:
These observations will remain integrated into major international reference networks, in particular the Network for the Detection of Atmospheric Composition Change (NDACC) and the European ACTRIS infrastructure, which coordinate global atmospheric composition monitoring. They will also continue to provide valuable validation data for satellite instruments and climate models used to evaluate policies for reducing greenhouse gas and pollutant emissions.
Thanks to this new instrument, researchers at ULiège will be able to continue documenting changes in the atmosphere year after year, distinguishing between natural and anthropogenic causes, and providing international bodies with the information they need to protect the climate and the ozone layer, both today and tomorrow.
"Au sommet du Jungfraujoch, l'ULiège surveille notre atmosphère depuis 70 ans", article by Christian Du Brulle, Dailyscience (February 22, 2023)
The new Fourier transform infrared (FTIR) spectrometer at the Jungfraujoch station was inaugurated on 27 November in the presence of Rector Anne-Sophie Nyssen, Emmanuel Mahieu and Pierre-Henri Lefèbvre (ULiège), SEM Patrick Van Gheel, Belgian Ambassador to Switzerland, Petra Zimmerman, Deputy Director of MeteoSwiss, Jörg Klausen (Federal Office of Meteorology and Climatology MeteoSwiss), Michelle Stalder (International Affairs Division, Swiss GAW/GCOS Office), Eliza Harris (Associate Professor, Climate and Environmental Physics, University of Bern and Director, High Altitude Research Stations Jungfraujoch and Gornergrat (HFSJG), Silvio Decurtins (President of the International Foundation High Altitude Research Stations Jungfraujoch and Gornergrat (HFSJG), Stefan Brönnimann, Chair of the Swiss GAW/GCOS Scientific Steering Committee
Professor Emmanuel Mahieu, Research Director, Fund for Scientific Research - FNRS
Co-financed by the Erasmus+ program and organized by the University of the Greater Region, this complementary training course worth 6 ECTS credits is open to all ULiège students.
All three scientists are members of the GIGA Institute and are receiving this grant for their ambitious projects in paediatric neuroscience and oncology.
ULiège offers its final-year Master’s students an exceptional opportunity: to join the Pan-European Seal Programme, a one-year paid traineeship programme within two prestigious international organisations.
