climate model simulations; climate dynamics; climate reconstructions; proxy data; data assimilation; past climate
Burgdorf Angela-Maria, Brönnimann Stefan, Franke Jörg (2019), Two types of North American droughts related to different atmospheric circulation patterns, in Climate of the Past
, 15(6), 2053-2065.
Brönnimann Stefan, Franke Jörg, Nussbaumer Samuel U., Zumbühl Heinz J., Steiner Daniel, Trachsel Mathias, Hegerl Gabriele C., Schurer Andrew, Worni Matthias, Malik Abdul, Flückiger Julian, Raible Christoph C. (2019), Last phase of the Little Ice Age forced by volcanic eruptions, in Nature Geoscience
, 12(8), 650-656.
Valler Veronika, Franke Jörg, Brönnimann Stefan (2019), Impact of different estimations of the background-error covariance matrix on climate reconstructions based on data assimilation, in Climate of the Past
, 15(4), 1427-1441.
Brönnimann Stefan, Frigerio Luca, Schwander Mikhaël, Rohrer Marco, Stucki Peter, Franke Jörg (2019), Causes for increased flood frequency in central Europe in the 19th century, in Climate of the Past Discussions
Labbé Thomas, Pfister Christian, Brönnimann Stefan, Rousseau Daniel, Franke Jörg, Bois Benjamin (2019), The longest homogeneous series of grape harvest dates, Beaune 1354-2018, and its significance for the understanding of past and present climate, in Climate of the Past Discussions
BrönnimannStefan (2019), Temps et climat en Suisse dans les années 1810 (Weather and climate in Switzerland in the 1810s), in Annales Valaisannes
, 2019, 49-60.
Delaygue Gilles, Brönnimann Stefan, Jones Philip D., Blanchet Juliette, Schwander Mikhaël (2018), Reconstruction of Lamb weather type series back to the eighteenth century, in Climate Dynamics
Brönnimann Stefan, White Sam, Slonosky Victoria (2018), Climate from 1800 to 1970 in North America and Europe, Palgrave Macmillan UK, London, 309-320.
CH2018 (2018), CH2018 – Climate Scenarios for Switzerland, Technical Report
, National Centre for Climate Services, Zurich.
Franke Jörg, Brönnimann Stefan, Bhend Jonas, Brugnara Yuri (2017), A monthly global paleo-reanalysis of the atmosphere from 1600 to 2005 for studying past climatic variations, in Scientific Data
, 4, 170076-170076.
Understanding the past behaviour of the climate system ideally relies on a comprehensive view of past climate states. However, paleoclimatology is often faced with a sparsity of proxies, and a comprehen-sive view is then only possible with audacious interpretation. In recent years, new numerical tech-niques have become available that derive a best estimate of the climate state by combining the real-world information from sparse proxy data with the physics of climate models. These data sets provide a physically consistent, spatially complete picture of the past climate system that is in agreement with the proxy records within their errors. In a just completed pilot project of the applicant, a 400-year long, monthly, global, 3-dimensional test data set was produced by assimilating historical instrumen-tal data, documentary evidence, and tree ring data into a large ensemble of climate model simulations using an off-line Ensemble Kalman Filter technique. While the feasibility of the approach and the usefulness of the resulting data set could be demonstrated, the potential still remains to be fully ex-ploited. The proposed project will create a new, 400-year data set through substantially improving the approach. It will systematically test some of the underlying assumptions, improve the incorporation of proxy data and their errors, optimize the specification of error covariances and provide a more sys-tematic validation. The resulting data set is expected to constitute a significant improvement over past reconstructions. The data will be used to study large-scale circulation changes associated with epi-sodes of slowed or accelerated warming, the transition from the Little Ice Age climate to the present climate, and the synchronism of northern and southern hemisphere, interannual-to-decadal climate.