News and Events



Representation of Extratropical Cyclones, Blocking Anticyclones, and Alpine Circulation Types in Multiple Reanalyses and Model Simulations

Reanalysis datasets are widely used in geosciences and thus their evaluation and intercomparison is crucial. In an effort to assess the mid-latitudinal atmospheric circulation, we compared the representation of blocks, cyclones and Central-European circulation types in a multitude of different reanalyses. The complete study by Marco Rohrer and colleagues finds a convergence for recent full-input reanalyses, although some metrics such as the depth of a cyclone still varies among datasets.



High-resolution assessment of the summertime urban heat load of Bern

In the context of the PhD project of Moritz Gubler, we recently established an extensive measurement network of about 80 low-cost temperature loggers within and around the city of Bern. Distributed over different urban structures, vegetation types as well as topographical and infrastuctural settings, the sensors placed within a self-made radiation shield will measure air temperatures every 10 minutes between May and September 2018. The goals of this project are to (1) assess the summertime urban heat island effect of the city of Bern at a very fine scale in order to create a data-base for (2) the validation of microscale urban climate models as well as (3) for future urban planning strategies taking into account the increasing importance of urban heat stress. Moreover, the results will be used for the (4) development and evaluation of teaching material focussing on local climate change. For further information or in case of questions, please contact Moritz Gubler (



Review of Early Twentieth Century Warming

From ca. 1900 to 1945 the globe warmed considerably, which has remained a mystery in climate sciences. In a new review article in WIREs Climate Change, Gabriele Hegerl and co-authors review the "early twentieth century warming". They find that both natural and anthropogenic forcings contributed, augmented by strong internal variability of the climate system. The early twentieth century warm period had distinct regional expressions, which is a reminder that also future episodes of pronounced internal variability will leave strong regional imprints. 



CERA-20C Reanalysis Paper

The new CERA-20C reanalysis was produced in the ERA-CLIM2 project and published on the website of European Centre for Medium-Range Weather Forecasts (ECMWF). It is a historical reanalysis that reaches back to 1900 and assimilates only air pressure and marine winds, but in contrast to all previous historical reanalyses, it is a coupled reanalysis, providing atmosphere, ocean, land, ocean waves and sea ice. The paper that describes the reanalysis is now published in the "Journal of Advances in Modeling Earth Systems"

An interactive visualisation was by created be the University of Bern.



ERC Advanced Grant for Climate Reconstructions

Stefan Brönnimann receives a grant of ca. 3 million Swiss francs from the European Research Council for the next five years. The goal of the project PALAEO-RA is to produce a comprehensive reconstruction of global climate of the past six centuries, a palaeo-reanalysis. The reconstruction will provide globally complete, three dimensional monthly fields of many variables and thus allows dynamical interpretations of past climate events. The project combines numerical modelling and mathematical techniques with historical documentary data and measurements, and dynamical analyses. 


New colloquium program now available

Please note the new program of the Colloquium in Climatology, Climate Impact and Remote Sensing during spring semester 2018. There will be many interesting talks and exciting discussions about various topics. Feel free to join the colloquium on wednesday at 14:15 in room 310, Hallerstrasse 10 according to the program.



Society and history imprint on climate data

Measurements of climate are also measurements of the needs of society. This becomes particularly clear when looking at the past. Economic, political and cultural factors have influence the climate observing system. Making use of this information could help to design climate services. This is what Stefan Brönnimann and Jeannine Wintzer argue in a short "Correspondence" in the current issue of "Nature". Climate data products are not just best estimates of physical variables, they are also societal products. Decision making can learn from both.



Neues Lehrbuch "Klimatologie"

Diese Woche erscheint beim Haupt Verlag das neue Lehrbuch "Klimatologie" von Stefan Brönnimann. Das Buch in der Reihe UTB basics erläutert die physikalischen Grundlagen der Klimatologie und darauf aufbauend die Zirkulation von Atmosphäre und Ozean und die daraus resultierenden Klimata. Der letzte Teil behandelt Klimavariabilität und Klimaänderungen sowie die der Klimaforschung zugrunde liegenden Methoden. Das Lehrbuch "Klimatologie" richtet sich an StudienanfängerInnen der Geographie, aber wird diese durch das ganze Studium begleiten. Viele Mitglieder der Gruppe für Klimatologie haben an dem Buch mitgearbeitet. Danke an alle!



Climate Atlas of the Altiplano

Weather on the Altiplano of Bolivia and Peru can be rough. Minimum temperatures below -3 °C are frequent, but to the south-east the weather is often hot and dry. Just how cold, how dry, and how hot? In the framework of the SNF-funded R4D-project DECADE, a climate atlas was produced for the Altiplano, which is now published in "Geographica Bernensia". It provides maps for mean climate and extreme indices for temperature and precipitation. It thus serves as a necessary baseline for risk management and the adaptation to future climate change in this region.



Effect of quality control on climate trends

When downloading climate data from existing data bases, we usually assume that they have undergone some quality screening. While this may be true, there may still be quality issues that are not easily detected with automatic quality control algorithms. In the SNF-funded R4D-project DECADE, Stefan Hunziker discovered many such issues in data from Bolivia and Peru. Once detected, some of them could be corrected, others led to the exclusion of stations from the data set. The resulting trend maps show substantial differences to those without applying this additional quality control. Besides generating a new, high-quality data set of meteorological measurements in the Altiplano, Stefan Hunziker packed his quality control experience into an R-code that can be used in other parts of the world. His paper just appeared in "Climate of the Past".


Weather reconstructions

How can we reconstruct the weather of the past? A video by Lucas Pfister and Lukas Meyer of the Climatology Group explains this. The product of this procedure are global, six-hourly three-dimensional weather data. In the framework of the FP7 project ERA-CLIM2, several reanalyses were generated. An interactive visualisation of the University of Bern allows investigating the CERA-20C reanalysis.



Climate Reanalyses and Services for Society

In the framework of the final assembly of the FP7 project ERA-CLIM2, the climatology group organised a public symposium on "Climate Reanalyses and Services for Society". The talks in the morning summarised the findings of the ERA-CLIM2 project, while in the afternoon the scope was widened. The presentations addressed future European space capabilities and reanalyses and addressed the role of climate services on the global, European, and the Swiss level.



Students Publish Reanalysis Case Studies

Historical reanalyses allow studying weather events far back in time. They cover more extremes than previous data sets and thus allow more robust statistics. But how good are these data sets? Only by analysing a sufficient number of extreme events individually, we can get an impression of the strengths and limitations of these data sets. Students of the "Seminar in Climatology" did exactly that. Small groups of students past analysed weather extremes - and continued to work even after the seminar was finished. The papers are now published in a special volume in "Geographica Bernensia". Great thanks go to all students who participated in the seminar and the book!



Researcher's night

More then 9000 visitors attended the "Researcher's Night" in Bern on 16 September, despite the cold and partly rainy weather. The climatology group presented the methods of weather reconstruction to the audience. A nice opportunity to get in touch with the public and explain our research. Many thanks go to all group members who helped to make this possible!



Shiny 5th floor

After three months of hard work - and three months of exile for the climatology group - the 5th floor shines in new splendour. Many thanks go to all who were involved in the renovation, who helped moving in and out, all who endured the exile and the 3rd floor people who hosted us.



New people

Franziska Hupfer has joined the Climatology group for a three month stay (mid-August to mid-November 2017). As a historian specialized in History of Science (MA ETH), she supports Stefan Brönnimann’s team to produce a survey of Swiss early instrumental meteorological measurements.



Thirty years of Montreal Protocol

On 16 September 1987, 197 states signed the Montreal Protocol on Substances that Deplete the Ozone Layer. Though constant efforts are necessary to amend the list of substances treated under the protocol and to monitor new compounds, the Montreal Protocol is a success story. Emissions of ozone depleting substances could be reduced strongly, contributing to the protection of the ozone layer. First signs of recovery appear, though the ozone hole still appears every year (the image shows the ozone hole on 11 Sep 2017) and the year-to-year variability is large. As many of the substances treated under the Montreal Protocol are strong greenhouse gases, the Montreal Protocol also made a major contribution to climate change mitigation. Read the article in the Tagesanzeiger.



Valuable Citizen Science Data

Scientific data collected by lay people, termed "Citizan Science Data", can supplement scientific approaches. In her Bachelor thesis, Daria Lehmann compared phenological data, i.e., data on the timing of plant phases, from MeteoSwiss with corresponding data obtained from two Citizen Science projects: PhaenoNet and OpenNature. Although the spatial distribution of the three data sets is different, the thesis shows that Citizen Science data give comparable results for some of the well-observed phenophases (read article in the "Tagesanzeiger" on 28 August). The project was a cooperation between the climatology group and GLOBE SWISS.



Yield losses in Switzerland for a "Year Without a Summer" scenario

The "Year Without a Summer" of 1816 triggered the last famine in Switzerland. Previous studies of the climatology group have focused on explaining the adverse weather conditions in 1816. In this study, Simon Flückiger has modeled the potential yield losses in 1816 and 1817 in Switzerland using a crop model. This formed the basis for a present-day "Year Without a Summer" scenario. The results, which are now published in "Environmental Research Letters" (, show substantial reductions in potential yields. Potato yields are reduced by 20-50%. Even larger losses are modeled for Maize, which was not yet common in 1816 but is an important crop today. The study, which emerged from close collaboration of different groups of the Oeschger Centre, also shows that socio-economic conditions are extremely relevant for explaining the local effects and the hardship suffered by the population. In isolation, the present Swiss agricultural system could arguably cope with the effects. However, for societies in a state of large vulnerability, such a scenario could still have major implications. On a global scale, a "Year Without a Summer" could have disruptive effects on the food system. 



Excursion: Climate Change Adaptation

How do we deal with flood risk, and will climate change alter the flood hazard? What are the challenges for agriculture when it comes to climate change? Are we prepared for increased frequencies of heat waves? From 19 to 30 June, eleven students dealt with these questions at the occasion of an excursion on climate change adaptation led by Stefan Brönnimann and Renate Auchmann. The excursion started in Prag, where flood protection was the main topic. In Brno, we visited an agroclimatological field site and a laboratory and were informed on drought management. At the last location, Vienna, we analysed strategies for reducing effects of urban heat waves and visited the intensively managed agricultural area north of Vienna.



Micrometeorological Field Course

From 12 to 16 June, students from University of Bern and ETH Zurich participated in the biannual field course in micrometeorology. The course took place at inforama Rütti in Zollikofen near Bern. Students engaged in making meteorological observations, measuring fluxes of carbon dioxide and water vapour with eddy covariance, determining light absorption within a canopy, and measuring carbon dioxide and temperature on bicycle rides. The excellent weather facilitated the field work.



Ozone hole and its recovery affect rain in tropical Pacific Islands

The ozone hole that opens each spring in the stratosphere over Antarctica has farther reaching consequences than previously thought. A study of the climatology group now finds that even rainfall in the tropical South Pacific Islands is affected. During the period of the largest Antarctic ozone loss, from the 1960s to the 1990s, rainfall increased in French Polynesia in spring and early summer. The region lies near the tip of the so-called South Pacific Convergenze Zone, one of the most intense rainbands on Earth. Using climate models that simulate stratospheric ozone chemistry as well as observations covering the past 60 years, the researchers demonstrated that the ozone hole leads to a high-pressure ridge off New Zealand, from where a wave-like circulation pattern stretches accross the South Pacific and affects the rainband. It is well established that the stratospheric ozone hole strengthens the westerly winds near the surface over the Southern Ocean, but effects on the tropics had so far not been demonstrated. Model simulations suggest that anticipated stratospheric ozone recovery over the next decades will reverse these effects.

Link to paper
Link to press release



Model-aided climate reconstructions

Jörg Franke and co-authors form the climatology group present the first monthly resolved three-dimensional global climate reconstruction for the past 400 years. It is based on assimilating historical measurements, documentary reports, and tree-ring data into a large set of climate model simulations. With this new, freely available data, which is now published in the Nature journal „Scientific Data“, science will gain new insights into climate variability, its causes and consequences. Droughts or effects volcanic eruptions can be studied in more detail than hitherto possible.

Model-aided climate reconstructions



DECADE project meeting

Last week, scientists from Peru and Bolivia visited the climatology group at the occasion of the annual meeting of the DECADE project (Datos climáticos y eventos extremos para el área central de los Andes, funded by the Swiss Development Corporation Agency and the Swiss National Science Foundation in the R4D programme). The goal of the project is to promote climate services in the Central Andes by improving the climate data record. By meticulously going into the details of the measurements, including numerous station visits, collection of metadata, and careful analysis, the project could achieve a much better quality of climate data over the Altiplano (see Stefan Hunziker's article in International Journal of Climatology). At the meeting, the group discussed the next steps: The production of an atlas of climate extremes, which will be published towards the end of this year.



A weather observer

For over 40 years, Christian Röthlisberger from Grossaffolteren has observed plant phenological phases and has kept a weather station. His meticulous observations are important also for climate research. The data have been collected by the climatology group as part of the BernClim network. Watch this TV documentary (in German): Want to observe plant phenological phases as well? Use our portal to enter your own observation.   



ERA-CLIM2 Reanalyses and Observations

Atmospheric reanalyses are among the most widely used data sets in geosciences and beyond. They are an important part of climate services and are used by decision makers. Generating atmospheric reanalysis, however, is a complex effort that involves the entire atmospheric and climate science community. The ERA-CLIM2 project, which is now in its final year and in which the climatology group was leading a workpackage, has prepared the ground for sustainable reanalysis operations. This involves observation data rescue, post-processing and re-processing of historical in-situ weather observations around the world and satellite climate data records; research and development of coupled assimilation methods, capable of including observations from different Earth system components (land surface, ocean, sea ice, atmosphere, chemical components, …); reanalysis production, and evaluation and uncertainty estimation, including visualisation and evaluation methods capable of indicating uncertainty in the reanalysis. One of the products, CERA-20C reanalysis (a coupled global reanalysis of atmosphere and ocean with 10-members back to 1900, generated from only surface observations), has recently been released on the ecmwf website. A successful test product has been generated that includes upper-air data: the ERA-PreSAT reanalysis from 1939-1967. Future reanalyses will be based on these efforts.

Brochure ERA-CLIM2 (PDF, 7.5 MB)



Snow shoe day

Last week, the three grops from the 5th floor enjoyed a snow shoe excursion to Col des Neigeux. Fabulous weather accomapined our trip to the Jura mountains. Our excursion was rounded-off by a hot coffee at the restaurant 'Les Gümmenen', where this group picture was taken. Thanks, Peter!



Warm mid-Holocene in the Mediterranean

A study of an Oeschger Centre team led by Oliver Heiri shows that during the mid-holocene, Mediterranean climate was considerably warmer than previous studies had suggested. The new temperature reconstruction was obtained from chironomids in the sediments of two lakes in the Apennines. Results are in very good agreement with climate model simulations, whereas earlier studies based on pollen had found much lower temperatures. Arguably, pollen-based reconstructions also reflect environmental effects other than temperature, such as moisture regimes, land use and fire. The study was published in Nature Geoscience (read more).



Reconstruction of Central European daily weather types back to 1763

A new paper by Mikhaël Schwander and co-authors was recently published online in the International Journal of Climatology. A weather type classification from MeteoSwiss was reconstructed back in time based on early instrumental data. The paper presents the method of reconstruction and the new classification (called CAP7) which covers the period 1763-2009. This time series is a unique dataset of weather patterns for the Alpine Region and Central Europe which offers the opportunity to analyse the climate variability over Switzerland and Europe for almost 250 years.

For more information or access to the data:

Schwander M, Brönnimann S, Delaygue G, Rohrer M, Auchmann R, Brugnara Y. 2017. Reconstruction of Central European daily weather types back to 1763.
Int. J. Climatol. doi: 10.1002/joc.4974.



Tambora article in Top 10

The article on the Tambora eruption and the Year without a Summer of 1816 that grew out of the 2015 Bern-Meeting was featured among the top 10 accessed articles of "WIRE's Climate Change" of the year 2016. Check it out, it is open access:



Happy Holiday Season



December 1916: Deadly Wartime Weather

One of the worst meteorological disasters in history took place in the southeastern Alps during the infamous winter of 1916/17. Avalanches following a massive snowfall event killed thousands of soldiers as well as civilians. Yuri Brugnara and Marcelo Zamuriano of the climatology group now provide a detailed reconstruction of the event based on a reanalysis and subsequent dynamical downscaling. Together with the climate historians Christian Rohr and Daniel Segesser, impacts of the event could be studied. This shows the potential of combining numerical techniques with historical documents.

The study will be presented by Christian Rohr and Stefan Brönnimann:
Wed, 7 Dec 2016, 12.15–13.00, Cantina, Haus der Akademien, Laupenstrasse 7, Bern

The study (in English, German, and Italian) can be downloaded here:



The Coldest Decade of the Millennium? How the cold 1430s led to famine and disease

At an Apéro two years ago, Oeschger Centre PhD students Chantal Camenisch, Kathrin Keller and Melanie Salvisberg got talking about a specific past climatic variation: the 1430s, possibly the coldest decade of the millennium in Europe. Out of this grew an international workshop, held in Bern, and a review paper led by the three young scientists. The work linked climatologists with historians, climate modelers with proxy scientists and encompasses a broad range of topics ranging from climate forcings (which do not seem to have been responsible) and internal variability to societal impacts and perceptions. The paper, which is published today, is featured by the European Geosciences Union. Read all about it:



Focus on Climate in Switzerland

Under the auspices of ProClim, a forum of the Swiss Academy of Sciences (sc.nat), the Swiss climate science community has produced a report that summarizes the relevant findings of IPCC's Fifth Assessment reports with respect to Switzerland as well as specific research on climate change in Switzerland. The climatology group has contributed to this report as well as to the underlying IPCC Assessment. The report "Brennpunkt Klima Schweiz – Grundlagen, Folgen und Perspektiven" is presented to the public today.



New project on Swiss historical climate observations

On 1 November 2016, project CHIMES ("Swiss Early Instrumental Measurements for Studying Decadal Climate Variability") started in the climatology group. The project, which is funded by the Swiss National Science Foundation is as cooperation with the Institute of History of the University of Bern and MeteoSwiss. The goal is to catalogue, image, and digitise meteorological measurements in Switzerland prior to 1864 (which is when the national network started), including several new series that reach back into the 18th or early 19th century. The new series will be evaluated with respect to decadal variability of weather and climate extremes, and an attempt will be made to produce gridded weather data products for Switzerland back to the early 19th century. As a first step, Lucas Pfister, Lukas Munz and Leonie Villiger now start to work on the catalogue.



Neues Buch: "Die Grindelwaldgletscher. Kunst und Wissenschaft."

Die beiden Grindelwaldgletscher gehören zu den am besten dokumentierten Gletschern der Welt, nicht zuletzt dank der Faszination, die sie auf Maler und Photographen im 18. und 19. Jahrhundert ausübten. Durch die Kombination von historischen Bild- und Schriftquellen mit glazialgeomorphologischen und dendrochronologischen Methoden lassen sich vergangege Vorstoss- und Rückzugsphasen oft jahrgenau untersuchen. In ihrem Buch zeichnen Heinz Zumbühl, Samuel Nussbaumer, Hanspeter Holzhauser und Richard Wolf die Entwicklung der beiden Gletscher über die letzten fünf Jahrhunderte nach und zeigen umfangreiches und einzigartiges Bildmaterial.

Buchpräsentation: «Als Gletscher noch Eis waren», am Dienstag, 25. Oktober im Alpinen Museum (



SCOSTEP Workshop

On 4-5 October, the 1st Swiss SCOSTEP (Scientific Committee on Solar-Terrestrial Physics) workshop was held in Bern, organised by the climatology group and Christoph Raible. 31 researchers came together to exchange their expertise in several disciplines ranging from fundamental solar physics, solar variability and its effects on Earth, in particular the climate system, to new measurement techniques and future satellite missions. The workshop successfully delivered an overview of the current activities within these communities and first synergies were identified which are aimed to result in joint research activities in the comings months and years.



New Project: PhenoClass

The Swiss Phenology Network comprises around 160 stations, however its quality and homogeneity has never been assessed comprehensively. The aim of this project is to develop a novel classification scheme for series and stations of the Swiss Phenology Network in close collaboration with MeteoSwiss.



Opening of World Nature Forum

Yesterday, the "World Nature Forum" in Naters, the visitor center of the UNESCO Swiss Alps Jungfrau-Aletsch World Heritage Site, was inaugurated in the presence of federal councillor Doris Leuthard, former federal councillor Adolf Ogi and representatives of politics and economics. In the interactive exhibitions the visitor will experience with all its senses the property and immerse into the thrilling and varying sceneries of the Alps. The Institute of Geography played an important role in the scientific design of the exhibit.




The climatology group is strengthening its collaboration with the LGGE (Laboratoire de glaciologie et géophysique de l'environnement) of the University Grenoble Alpes. The group visited the Gilles Delaygue and Martin Wegmann at LGGE for a two-day excursion and enjoyed both exciting science and an exciting scenery.