A century of column ozone monitoring: Uncovering the recovery

A new, long column ozone series from Oxford helps better separating chemical and dynamical influences on the ozone layer. This shows that the recovery of the ozone layer, though not seen in mid-latitude observations, is underway but masked by changes in atmospheric dynamics. This is the conclusion of a paper by Stefan Brönnimann that has been published in "Communications Earth & Envorinment".

«Dieser Sommer gibt uns zu denken»

Bereits in Juni purzeln Rekorde, Bern hatte schon mehrere Tropennächte, die Emme kein Wasser. Im Berner Podcast "Gesprächsstoff" ist die aktuelle Hitze das Thema - und wie man sich vor Überhitzung schützen kann.

https://www.bernerzeitung.ch/die-schattenseite-der-verfruehten-hitzewelle-184125994774

More floods in a warmer world

Palaeoclimate studies suggest that past flood-rich periods coincided with cool periods, while climate projections suggest that flood risk may increase in a warming world. A contradiction? A new paper by the climatology group addresses this question by partitioning atmospheric drivers of floods into circulation changes and water vapour changes. Frequent floods in Europe in the mid 19th and early 20th century, as well as the flood-poor period in the mid 20th century, were driven by changes in atmospheric circulation. Conversely, the recent increase in flood frequency was driven by an increase in water vapoour, which in turn is driven by increasing temperature.

https://doi.org/10.5194/cp-18-919-2022

Winters are 3°C warmer than pre-industrial

Temperature reconstructions for the cold season based on freezing and thawing data from rivers and the observation of plants show the extent of warming over the past 300 years. Reconstruction show that northern mid-latitudes have warmed by three degrees. The new data also allow a better analysis of climate mechanisms. Particularly, the point to the important role of snow cover. These are the results of a study by the Climatology Group published today in “Nature Communications”.
https://www.nature.com/articles/s41467-022-29677-8

Climate data mirror world history

The collaboration between climate scientists and historians has a long tradition. Work on historical measurements is a prime example how developments on the two disciplines can further stimulate the mutual benefit. Historian Chantal Camenisch and climatologist Stefan Brönnimann discuss their views in a NZZ article (https://www.nzz.ch/wissenschaft/was-wetterdaten-ueber-die-weltgeschichte-verraten-ld.1592087). Also non-scientists can contribute to gaining climate data. A recent Euronews feature with Stefan Brönnimann addresses the role of citizen science in climate research.

Documentary on 50 Years of Climate Research

Climatology professor Stefan Brönnimann made a on 50 years of climate research at the Institute of Geography. The result is a very personal portrait of Bernese pioneers and an impressive piece of scientific history. It shows how personal leadership and passion lead to groundbreaking international research, local to international research programs and astonishing careers. The documentary is freely available in German and Swiss German with English subtitles. Link to the movie: www.youtube.com/watch?v=rcjEkEPX5xE

A treasure much bigger than previously thought

New numerical methods can make use even of short meteorological measurement series to produce global weather reconstructions far back in time. These short records have not received much attention so far. According to a study led by Stefan Brönnimann and published in the "Bulletin of the American Meteorological Society", there are thousands of such records in archives and libraries worldwide prior to the start of National Weather Services, enabling new insights from past weather.
Link: https://journals.ametsoc.org/doi/full/10.1175/BAMS-D-19-0040.1

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.

Historical weather diaries as a basis for climate research

Historical weather observations help to understand atmospheric processes behind weather and climate events. The weather diary of the Kirch family from Berlin covers almost a century and provides the basis for the longest measurement series in Germany. In his Sabbatical, Stefan Brönnimann photographed the diary in Berlin. In this video he explains his work.

earth@PALAEO-RA: Animated monthly maps back to 1600

The latest monthly paleo-reanalyses data by Veronica Valler and colleagues are now available as visualizations in the Earth animator of global weather conditions. By selecting among 7 different variables, the user can visualize features such as low-level winds, the jet stream, temperature of precipitation. Input for the reanalysis of EKF400v2 uses a greatly extended observational network of early instrumental temperature and pressure data, documentary evidences and tree-ring width and density proxy records.

Andrew Friedman joins PALAEO-RA as Marie Curie Fellow

Dr. Andrew Friedman will join the PALAEO-RA team with a prestigious Marie-Skłodovska Curie individual fellowship. Physical geographer and climatologist by training, Andrew's project “AQUATIC” (Assessing and QUantifying the ATlantic Instrumental hydroclimate) will compile recently-recovered measurements of precipitation, river discharge, and surface salinity from different archival sources to develop an integrated record of tropical Atlantic regional hydroclimate back to the late 19th century. The tropical Atlantic basin contains the world’s largest river systems and rainforests, growing populations with global warming having projected impacts on the hydroclimate including rainfall and river flow.

Swiss historical meteorological records

Did you know that in Switzerland, prior to the start of MeteoSwiss in 1863, over 330 meteorological records from over 200 locations were measured? Within the successfully concluded project CHIMES (funded by the Swiss National Science Foundation) and the ongoing projects "Long Meteorological Series" (GCOS) and PALAEO-RA (ERC), these measurements were rescued. A detailed inventory was produced and imaged data sheets and the digitised data were published in public repositories. A first series of papers, most of them written by students, is now published in "Geographica Bernensia". Each paper describes the historical information on one of the series. A second series of papers on further series will follow. These data will form the basis for a daily weather reconstructions of the past centuries and for the generation of a set of ca. 10 long homogenised Swiss series.

Two types of North American droughts related to different atmospheric circulation patterns

The western USA is frequently affected by multi-annual summer droughts. They can be separated into two groups with distinct spatial patterns, often termed Dust Bowl-type droughts and 1950s-type droughts. Contributing to the PALAEO-RA project, a recently published study by Angela-Maria Burgdorf, Stefan Brönnimann and Jörg Franke of the climatology group analyzes the atmospheric circulation during these multi-annual drought events in a novel global monthly three-dimensional reconstruction of the atmosphere back to 1600 ( EKF400). Results confirm the two distinct drought types and show that they differ with respect to atmospheric circulation as well as sea surface temperatures. These insights may be useful in the context of drought prediction and analysis. The paper was published in the journal Climate of the Past.

Volcanoes shaped the climate before humankind

A new study by Stefan Brönnimann and co-authors published in Nature Geosciences shows that the pre-industrial climate was not constant: if one takes the cold period of the early 19th century as the starting point for current global warming, the climate has already warmed up more than assumed in the current discussions. “Given the large climatic changes seen in the early 19th century, it is difficult to define a pre-industrial climate,” explains lead author Stefan Brönnimann, “a notion to which all our climate targets refer.” Five large volcanic eruptions occurred in the early 19th century. They caused cooling, drying in the monsoon regions and glaciers growing in the Alps.

Changing causes of climate change since 1750

Large-scale climate changed dramatically between 1750 and today. A new paper by Gabriele Hegerl with PALAEO-RA contributions reviews the causes for climatic changes over this period. It shows how greenhouse gases began to cause warming since the beginning of industrialization, dominating recent trends. Other forcings have caused substantial deviations from this trend: volcanic eruptions led to strong episodic cooling. Anthropogenic aerosol forcing most likely masked some global greenhouse warming and influenced regional temperatures, monsoons and Atlantic variability. Long-term precipitation changes are more difficult to attribute to external forcing, but the observations support modeled changes. The paper "Causes of climate change over the historical record" was published in Environmental Research Letters.

Old weather “time machine” opens a treasure trove for researchers

This month, a NOAA-funded research team including Stefan Brönnimann and the PALAEO-RA project published an update to a weather “time machine”. This third version of the 20th Century Reanalysis Project is a dauntingly complex, high-resolution, four-dimensional reconstruction of the global climate that estimates what the weather was for every day back to 1836. The data are now publicly available. Read the an concise report in National Geographic: http://bit.ly/OldWeatherTimeMachine

Climate Data Rescue Supports Climate Services in Africa

In some regions of the world, climate projections are not particularly reliable. Even current climate may not be well specified, while climate data would be particularly valuable for decision making. Some African countries face the problem that many long climate records are known but inaccessible for various reasons. A recent story in "Nature" explains why this is the case and points to the value of data rescue. With contribution of the PALAEO-RA project to the Copernicus Climate Change Services (C3S), Data Rescue Services will provide a platform for such activities. This was also acknowledged at the C3S General Assembly held the last week in October in Warsaw, Poland.

Keynote speakers at the Swiss Climate Summer School 2020

Stefan Brönnimann and Jörg Franke from the PALAEO-RA project will give a keynote talk at the 19th Swiss Climate Summer School in Grindelwald, Switzerland, from 23–28 August 2020. Entitled «Extreme weather and climate: from atmospheric processes to impacts on ecosystems and society» in 2019, the Summer School annually attracts PhD and early PostDoc students from around the world. Other speakers include Thomas Stocker, Naomi Oreskes and Christian Otto. Register now.

Climate is changing the flavor of wine

"Records going back 700 years show that Burgundy’s wine grapes have been feeling the heat of the past three decades." The story in the latest issue of National Geographic is partly based on new research by Thomas Labbé with contributions from Stefan Brönnimann. Read the complete story how the wine is changing.

Quantifying the role of the Tambora eruption in the 1816 ‘year without a summer’

A new study estimates for the first time how the eruption changed the probability of the cold and wet European ‘year without a summer’ of 1816. The group around Andrew Schurer form the University of Edinburgh combined model simulations with climate reconstructions using a so-called detection and attribution technique. They found that the observed cold conditions were almost impossible without the eruption, and the wet conditions would have been less likely. The paper appeared today in "Environmental Research Letters".

Fastest warming in the last 2,000 years

In contrast to pre-industrial climate fluctuations, current, anthropogenic climate change is occurring across the whole world at the same time. In addition, the speed of global warming is higher than it has been in at least 2,000 years. That’s according to two studies published in Nature from the University of Bern with contributions from Stefan Brönnimann and Jörg Franke of the PALAEO-RA team.

Version 3 of "Twentieth Century Reanalysis" published

The atmospheric reanalysis 20CR that is based only on surface and sea-level pressure information and which reaches back to the 19th century, has become widely used data set. Version 3 of this reanalysis is now published. It is based on an improved assimilation system, has a higher resolution, more ensemble members and reaches back to 1836. The paper by Laura Slivinski from University of Colorado and NOAA and co-authors including Stefan Brönnimann is now published in the Quarterly Journal of the Royal Meteorological Society.

Flood-prone weather types caused increased flood frequency

Increased flood frequencies and their causes in the the mid- and late 19th century have been discussed intensely. A team of researchers led by Stefan Brönnimann now found the causes of the increase in the 19th century and a decreased frequency after the Second World War in central Europe. The researchers used daily weather type classifications back to 1763 to reconstruct flood probability indices. The findings agree with independent circulation reconstructions that indicate increased cyclonic flow over western Europe in the former period and flood-prone weather types. In climate simulations, there is no increase in the Rhine catchment in the 19th century but a decrease in the post-war period that could have been related to sea-surface temperature anomalies.

Reducing the effect of sampling error in climate reconstructions based on data assimilation

Data assimilation combines climate observations with an ensemble of model simulations to obtain climate reconstructions. The background-error covariance matrix determines how the information from observations spreads into model space. But what are the best estimates of this matrix from a small ensemble? Veronika Valler, Jörg Franke and Stefan Brönnimann tested different methods to reduce the effect of sampling error. Recently published in Climate of the Past, the researchers found that blending the covariance matrix calculated from the model ensemble for the target year with a "climatological" one based on a large, random sample of all model years leads to a improved reconstructions.

334 entries of Swiss Early instrumental series

The Swiss meteorological network was established in 1864, but scientists, doctors, priests, and lay persons measured the weather already much earlier. Some of these efforts were organised by Natural Science Societies, some were private undertakings. But how dense was the network prior to 1864? The systematic catalugue of per-1864 Swiss meteorological records produced by Lucas Pfister and published in "Climate of the Past" reveals astonishing 334 entries from 206 locations. Most of these records have now been imaged and are made publicly available at https://doi.org/10.5281/zenodo.3066836

Summer weather 2019

Der Wetterdienst «wetter.com» warnt vor einem weiteren Hitzesommer, ein Berner Klimatologie Professor zweifelt an der Genauigkeit der Prognose. Er warnt aber auch: Die Sommer in der Schweiz werden immer heisser.

e-learning: From historical climate data to hazard maps

Stefan Brönnimann from the PALAEO-RA project of the Institute of Geography has released an e-learning tool for weather reconstructions. On www.weather-reconstruction.org, students and anyone interested can learn step-by-step how historical manuscript data can eventually lead to complex climate information such as hazard maps. The tool focuses on sources of uncertainty and the application of reanalysis data and other data products in a meaningful way. Data can be downloaded for analyses in statistical software and visualization tools. The sections Climate Data, Global Reanalyses and Downscaling and Applications each starts with a very short text and the video followed by 2-4 subsections, typically with an exercise.

PALAEO-RA website is online

A comprehensive overview of the PALAEO-RA-project is now accessible online. On www.palaeo-ra.unibe.ch, we have compiled the most important information about the project, members, outcome, news and publications. A specific page will make available all the data from historical input data to simulations and reanalyses. Enjoy surfing: www.palaeo-ra.unibe.ch

Grape harvest date of the last half millennium

Since the hot summer 2003, 8 out of 16 spring-summer periods were outstanding according the statistic of the last 664 years. In the Paris temperature measurements since 1659, April-to-July temperature reached the highest value ever in 2018. New research from interdisciplinary team of historians and climatologists including Stefan Brönnimann from PALAEO-RA project shows demonstrates that outstanding hot and dry years in the past were outliers, whereby they became the norm since the transition to rapid Global Warming in 1988. After that year, harvests began 13 days earlier than the period before when harvest dates averaged on September 28. Under the lead of Thomas Labbé, the scientists reassessed grape harvest dates from original archival sources rather than nineteenth century publications. The study has just been accepted for publication in Climate of the Past.

New e-learning videos online

Three e-leraning videos from the Climatology research group are newly available online. The first video describes in-depth how we come from historical weather observations to homogeneous time series of meteorological variables. The second video explains how global weather reconstructions are generated from local weather time series. The third video describes methods to generate local weather reconstructions from global weather reconstructions.

New people in the PALAEO-RA team

On 1 October the ERC Advanced Grant project "A Palaeoreanalysis To Understand Decadal Climate Variability" (PALAEO-RA) has started in the climatology group.

Team complete

Dr. Ralf Hand and Elin Lundstad are the latest team members of PALAEO-RA. Ralf did his PhD on midlatitude ocean-atmosphere interactions at the GEOMAR Helmholtz Centre for Ocean Research in Kiel. He will work in the modeling part of the PALAEO-RA project.

Elin started as a PhD student at GIUB in April 2019. She has worked for the Norwegian Meteorological Institute and the Norwegian hydropower company Statkraft. Her PhD project within PALAEO-RA is on “Variability of weather and climate since 1700 from early instrumental observations”.