Jürgen Herget

The year-long unprecedented European heat and drought of 1540 – a worst case

The heat waves of 2003 in Western Europe and 2010 in Russia, commonly labelled as rare climatic anomalies outside of previous experience, are often taken as harbingers of more frequent extremes in the global warming-influenced future. However, a recent reconstruction of spring–summer temperatures for WE resulted in the likelihood of significantly higher temperatures in 1540. In order to check the plausibility of this result we investigated the severity of the 1540 drought by putting forward the argument of the known soil desiccation-temperature feedback. Based on more than 300 first-hand documentary weather report sources originating from an area of 2 to 3 million km2, we show that Europe was affected by an unprecedented 11-month-long Megadrought. The estimated number of precipitation days and precipitation amount for Central and Western Europe in 1540 is significantly lower than the 100-year minima of the instrumental measurement period for spring, summer and autumn. This result is supported by independent documentary evidence about extremely low river flows and Europe-wide wild-, forest- and settlement fires. We found that an event of this severity cannot be simulated by state-of-the-art climate models.

Megaflood sedimentary valley fill: Altai Mounatins, Siberia

During the Quaternary, the Altai Mountains of south-central Siberia sustained ice-caps and valley glaciers. Glaciers or ice lobes emanating from plateaux blocked the outlet of the Chuja-Kuray intermontane basins and impounded meltwater to form large ice-dammed lakes up to 600 km3 capacity. On occasion the ice dams failed and the lakes emptied catastrophically. The megafloods that resulted were deep, fast-flowing and heavily charged with sand and gravel, the sediment being sourced from the lake basins and also entrained along the course of the flood-ways. The floods were confined within mountain valleys of the present-day Rivers Chuja and Katun, but large quantities of sediment were deposited over a distance of more than 70km from the dam site in tributary river-mouths, re-entrants in the confining valley walls (e.g. cirques) and on the inside of major valley bends. The main depositional units that resulted are giant bars which blocked the entrances to tributaries and temporarily impeded normal drainage from the tributaries into the main-stem valley such that minor lakes were impounded within the tributaries behind the bars. Fine sediment from the tributaries accumulated in these lakes as local lacustrine units. Later the bars were breached by the tributary flows and the local lakes were drained. Sections of the giant bar sediments and the local lacustrine units are used to describe the nature of the megaflood valley fill which was deposited primarily in Marine Isotope Stage 2. Although there is evidence of the Chuja-Kuray lake being in existence within Marine Isotope Stage 4 there are no flood sediments unequivocably ascribed to this period. Descriptions of the sedimentology and stratigraphy of the valley-fill are interpreted within a context of proposed flow mechanisms associated with deposition of the various facies and thus provide some indication of the flood dynamics

Obstacle-Reynolds-number based analysis of local scour at submerged cylinders

A simple process-based, analytical approach is developed and validated herein to determine the local scour at obstacles in the fluvial environment. It is based on the obstacle Reynolds and Froude numbers. Clear-water flume experiments were conducted to investigate the local scour depths at submerged cylinders in coarse uniform sand. The resulting scour depths were correlated with an analytical model and validated with two data sets on local scour at submerged and emergent cylinders. The size of the projected frontal obstacle area in relation to the mean flow velocity has a significant effect on the scour hole shape and depth. A power law function is derived that satisfactorily describes the present scour depth data. The approach is limited to near-equilibrium clear-water scour, uniform sediment and excludes particle density effects.

Tree-rings and people – different views on the 1540 Megadrought. Reply to Büntgen et al. 2015

Buntgen et al. (2015; hereinafter B15) present the result of new research which question the results of Wetter et al. 2014, (hereinafter W14) and Wetter et al. (2013, hereinafter W13)regarding European climate in 1540. B15 conclude from tree-ring evidence that the results based on documentary data of W14 probably overstated the intensity and duration of the 1540 drought event. W14 termed it Megadrought because of its extreme duration and spatial extent compared to other drought events in central Europe, although they note that the term is generally used for decadal rather than for single-year droughts (Seneviratne et al. 2012). We take the opportunity to recall the following issues. Firstly, when dealing with drought the complexity of this phenomenon should be kept in mind. Meteorological drought defined as a large negative precipitation anomaly during a certain period can trigger agricultural, hydrological, groundwater and socioeconomic droughts. Lloyd-Hughes (2013] and references cited herein) concluded that any workable objective definition of drought does not exist. To quantify droughts, various indices based on precipitation, temperature and evapotranspiration are used such as the Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Z-index and PDSI. Their calculation depends on different periods (seasons, combination of months) and so different indices may classify the same drought episode differently (e.g. Brazdil et al.2014).

Extreme Events in the Geological Past

Many Xevents in the geological past exceeded the strengths and intensities observed for modern-day natural events. The number of extraordinary events that occurred in the geological past is of course much larger than the number we witness today because the geological timescale covers millions of years. This contribution focuses on these Xevents from earth’s geological history, including selected examples from plate tectonics, earth magnetism, ice age cycles, volcanism, earthquakes, meteorite impacts and floods. Events related to these processes occur on different timescales. For example, drastic modifications of atmospheric and oceanic circulation due to continental shift (which creates new mountain ranges and reshapes land masses and oceans) take millions of years, while meteorite impacts happen within seconds. However, any these processes can be the trigger for dramatic consequences, like mass extinctions of life, or global glaciations. An overview of a research program that considers historic and prehistoric flood events is given. Based on the water levels observed during floods, the palaeodischarge can be determined and used to improve the reliability of flood predictions. Investigations of Pleistocene ice-dammed lake outburst floods (the largest flood events in the Earth’s history) are useful when developing new methods and techniques that can be applied to younger events of a smaller scale in other environments.

Zur Geochemie der Böden industriell geprägter urbaner Gebiete

Die Boden in Siedlungsgebieten industriell gepragter Ballungsbereiche sind stark anthropogen uberpragt. Sie enthalten anorganische und organische Fremdstoffe, die vereinzelt fur Pflanzen und Menschen toxische Konzentrationen erreichen (→ Kap. 10). Die Quantifizierung flachiger Belastungen mit Schwermetallen begann vor nur etwa 20 Jahren (Kramer 1976). Auf die ebenfalls grosflachigen Belastungen mit z.T. chlorierten polyaromatischen Verbindungen wurde man sogar erst vor etwa zehn Jahren u.a. durch die Folgeprobleme der Bebauung von industriellen Altstandorten aufmerksam (Fuhr et al. 1986; Hembrock 1988; Konig u. Hembrock 1989). Zuvor standen allein die visuell und geruchlich wahrnehmbaren Belastungen der Luft und der Oberflachengewasser im Vordergrund des Interesses von Bevolkerung und Politikern sowie kommunalen und staatlichen Verwaltungen. Im Gegensatz zu Luft und Wasser konservieren Boden jedoch ihre einmal erhaltenen Belastungen durch persistente Stoffe und sind daher meist irreversibel kontaminiert. Bodenuntersuchungen wurden schon seit den 60er Jahren durchgefuhrt, konzentrierten sich jedoch auf ausgewahlte Schwermetalle und die polycyclischen aromatischen Kohlenwasserstoffe in Folge der Klarschlammanwendung auf landwirtschaftlich genutzten Flachen.

Erratum to: The year-long unprecedented European heat and drought of 1540 – a worst case

Oliver Wetter & Christian Pfister & Johannes P. Werner & Eduardo Zorita & Sebastian Wagner & Sonia I. Seneviratne & Jurgen Herget & Uwe Grunewald & Jurg Luterbacher & Maria-Joao Alcoforado & Mariano Barriendos & Ursula Bieber & Rudolf Brazdil & Karl H. Burmeister & Chantal Camenisch & Antonio Contino & Petr Dobrovolný & Rudiger Glaser & Iso Himmelsbach & Andrea Kiss & Oldřich Kotyza & Thomas Labbe & Danuta Limanowka & Laurent Litzenburger & Oyvind Nordli & Kathleen Pribyl & Dag Retso & Dirk Riemann & Christian Rohr & Werner Siegfried & Johan Soderberg & Jean-Laurent Spring