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Workshop on Extreme Climate Events: From Physics to Solutions Riederalp, Switzerland, March 24-28, 2015 Workshop Program Abstracts Volume List of Participants Climate extremes, adaptation and policy (from Physics to Solutions) Riederalp, Switzerland, March 24-28, 2015 Workshop Program TUESDAY, March 24 Afternoon and evening: arrival of participants¨ 19:15 Evening meal WEDNESDAY, March 25 08:4509:00 Opening remarks, structure and objectives of the workshop M. Beniston, M. Stoffel SESSION 1: HEAT/COLD WAVES AND RELATED IMPACTS 09:0009:30 09:3009:50 09:5010:10 10:1010:30 Current and future European heat waves in a historical perspective; insights from instrumental, model and proxy data Projected changes in the variability and extremes of European summer temperatures Influence of soil moisture on summer air temperature The impact of land-atmosphere interactions on North American temperature extremes as simulated by the Canadian RCM (CRCM5) 10:30 Coffee, tea, refreshments 11:0011:20 11:4012:00 12:0012:20 12:2012:40 Projected changes to hot/cold spell characteristics over Canada based on a Regional Climate Model ensemble Increases of Tmax to Tmin ratios despite a slowdown in mean temperature increases in Europe Extreme events and their impacts as seen from documentary sources in the last 500 years Reconciling reconstructions and simulations of volcanic cooling Climate warming, permafrost melting and enhanced rock-fall activity 12:45 Lunch and afternoon activities (ski, hiking, etc.) 11:2011:40 CHAIR: Markus Stoffel J. Luterbacher (Keynote) Abstract Vol. Page 1 J. Cattiaux Abstract Vol. Page 1 M. Gera Abstract Vol. Page 2 G. T. Diro Abstract Vol. Page 2 University of Giessen, Germany D. I. Jeong Abstract Vol. Page 3 University of Quebec at Montreal, Canada M. Beniston Abstract Vol. Page 3 University of Geneva, Switzerland R. Garcia-Herrera Abstract Vol. Page 4 S. Guillet Abstract Vol. Page 4 M. Stoffel Abstract Vol. Page 5 Universidad Complutense, Madrid, Spain University of Berne, Switzerland University of Geneva, Switzerland SESSION 2: HEAVY PRECIPITATION, DROUGHT, AND HYDROLOGICAL RESPONSES (1) 17:1517:45 18:0518:25 A consistent picture of the hydroclimatic response to global warming from multiple indices: Models and observations The contributions of soil-moisture interactions to future changes in the characteristics of daily precipitation in CMIP5 projections Climate extremes in an ensemble of CORDEX regional climate scenarios for Europe 18:30 End of Day 1 18:45 Icebreaker followed by evening meal 17:4518:05 University of Geneva, Switzerland F. Giorgi (Keynote) Abstract Vol. Page 5 W. May Abstract Vol. Page 6 C. Corona Abstract Vol. Page 6 Météo-France, Toulouse University of Bratislava, Slovakia University of Quebec at Montreal, Canada CHAIR: David Stephenson A. Salaam International Centre for Theoretical Physics, Trieste, Italy University of Lund, Sweden Blaise Pascal University, Clermont-Ferrand, France THURSDAY, March 26 SESSION 2: HEAVY PRECIPITATION, DROUGHT, AND HYDROLOGICAL RESPONSES (2) CHAIR: Martin Beniston 08:3009:00 09:0009:20 Drought and hydro-climate variability in the western Americas Assessing small scale heavy precipitation from stability indices in RCMs B. Luckman (Keynote) Abstract Vol. Page 7 D. Leidinger Abstract Vol. Page 7 09:2009:40 09:4010:00 C. Siderius Abstract Vol. Page 8 S. Allen Abstract Vol. Page 9 10:0010:20 10:2010:40 Shifts in extreme events in the Hindu Kush–Himalaya (HKH) region Rainfall and snow-melt triggered glacial lake outbursts: a systematic analysis of the June 2013 Kedarnath disaster (Uttarakhand, India) Extreme hydro-meteorological: A study of two successive flash floods in the Central Himalayas Understanding extreme flood events in ungauged mountain streams and their links to climate change University of Western Ontario, London, Canada University of Natural Resources and Life Sciences, Vienna, Austria University of Wageningen, The Netherlands Universities of Geneva and Zurich, Switzerland M. Arora Abstract List Page 9 J. Ballesteros Abstract Vol. Page 10 National Institute of Hydrology, Roorkee, India Universities of Geneva and Berne, Switzerland 10:40 Coffee, tea, refreshments 11:1011:30 11:3011:50 11:5012:10 12:1012:30 Use of historical sources in a study of the hydrometeorological extremes in the Danube River Basin Increasing of severe hydrological events in the Po basin under global warming Scenarios of changes in local precipitation extremes for the Netherlands Drought frequency in the last 3 centuries in the Moscow region from pine and oak ring width chronologies M. Melo Abstract Vol. Page 11 B. Tomassetti Abstract Vol. Page 11 G. Lenderink Abstract Vol. Page 12 O. Solomina Abstract Vol. Page 12 University of Bratislava, Slovakia University of L’Aquila, Italy 12:30 Lunch and afternoon activities (ski, hiking, etc.) 17:3018:45 Discussion session 1 DISCUSSION LEADER: Filippo Giorgi Revisiting the day’s presentations Implications for adaptation and policy Looking to the future; joint collaboration and beyond (Horizon-2020, etc.) 18:45 End of Day 2 19:15 Evening meal (surprise event!) KNMI, De Bilt, The Netherlands Russian Academy of Sciences (Geography/Glaciology), Moscow, Russian Federation FRIDAY, March 27 SESSION 3: WIND STORMS AND RELATED EVENTS 08:3009:00 How extreme can storms become? 09:0009:20 09:2009:40 09:4010:00 10:0010:20 Dynamical downscaling of historical windstorms for modeling wind hazard in Switzerland Severe rain, hail, lightning and the number 42 10:20 Coffee, tea, refreshments Climate extremes in an ensemble of CORDEX regional climate scenarios for Europe Coastal hazards and Mediterranean storms CHAIR: Erich Fischer D. B. Stephenson (Keynote) Abstract Vol. Page 13 P. Stucki Abstract Vol. Page 13 B. Ahrens Abstract Vol. Page 14 E. Kjellström Abstract Vol. Page 14 P. Lionello Abstract Vol. Page 15 University of Exeter, United Kingdom University of Berne, Switzerland University of Frankfurt, Germany SMHI, Norrköping, Sweden University of Salento and CMCC, Lecce, Italy SESSION 4: METHODOLOGIES FOR STUDYING EXTREMES (STATISTICAL METHODS, ETC.) 10:5011:20 11:2011:40 11:4012:00 12:0012:20 12:2012:40 Robust Forced Signals and Irreducible Uncertainties in Projections of Extremes Evaluating simulated precipitation extremes 12:45 Lunch and afternoon activities (ski, hiking, etc.) 17:3018:45 Discussion session 2 DISCUSSION LEADER: Brian Luckman Revisiting the day’s presentations Implications for adaptation and policy Looking to the future; joint collaboration and beyond (Horizon-2020, etc.) 18:45 End of Day 3 19:15 Evening meal Heat waves over Central Europe in ENSEMBLES and CORDEX RCMs: past biases and future uncertainties Impact of daily temperature homogenization on cold extreme indices in Switzerland Hierarchical Bayesian space-time modelling to infer climatic trends from extreme events in mountainous environments E. Fischer (Keynote) Abstract Vol. Page 15 A. Toreti Abstract Vol. Page 16 O. Lhotka Abstract Vol. Page 16 R. Auchmann Abstract Vol. Page 17 N. Eckert Abstract Vol. Page 18 ETH-Zurich, Switzerland Joint Research Centre (JRC), Ispra, Ialy Global Change Research Center, Brno, Czech Republic University of Berne, Switzerland IRSTEA, Saint-Martind’Hères, France SATURDAY, March 28 SESSION 5: LINKS TO POLICY 08:3009:00 09:0009:20 09:2009:40 09:4010:00 Modelling Climate Change and Socioeconomic Pathways in the Ganges and Brahmaputra River Systems Extreme floods in mountain valleys – towards a physically-based warning system Adaptation to river floods, today and tomorrow Analysis of extreme climatological events in the Carpathian region for regional adaptation planning CHAIR: Olga Solomina P. Whitehead (Keynote) Abstract Vol. Page 18 B. Brock Abstract Vol. Page 19 Z. Kundzewicz Abstract Vol. Page 19 J. Bartholy Abstract Vol. Page 20 University of Oxford, United Kingdom Partner Re Reinsurance Com-pany, Zurich, Switzerland University of Zurich, Switzerland University of Northumbria, Newcastle, United Kindom Polish Academy of Sciences, Poznan, Poland Eötvös-Lorand University, Budapest, Hungary 10:00 Coffee, tea, refreshments 10:3010:50 Windstorm loss models, state of the art, challenges and future directions P. Della Marta Abstract Vol. Page 20 10:5011:10 Attribution of loss and damage to climate change and implications for climate policy C. Huggel Abstract Vol. Page 21 11:1512:30 Discussion session 3 (Wrap-up session) DISCUSSION LEADER: Martin Beniston Revisiting the day’s presentations Joint publications (Special Issues)/Review papers, etc., from this meeting: journal(s), timelines, etc. Preparation of a policy brief (for example in advance of COP-21 in Paris)? Looking to the future; joint collaboration and beyond (Horizon-2020, etc.) Any other business 12:3012:40 Closing remarks and farewell 12:45 End of the RIEDERALP-2015 WORKSHOP M. Beniston and M. Stoffel University of Geneva, Switzerland VOLUME OF ABSTRACTS List in the order of appearance of the contributions as given in the workshop program Riederalp-2015 Abstracts Volume Current and future European hot summers and heat waves in a historical perspective; insights from instrumental, model and proxy data Juerg Luterbacher et al. Justus Liebig University of Giessen, Germany [email protected] The summers of 2003 and 2010 were exceptionally warm and dry in large parts of Europe and western Russia, respectively and caused adverse impacts and ten thousands of dead people. Regional multi-model experiments indicate that the probability of such European scale summers experiencing ‘mega-heatwaves’ will increase strongly within the second half of the 21st century. Recent advance in statistical reconstruction methods, interpreting new documentary and natural climate proxy evidence allow a better insight into past spatiotemporal high resolution climate/extremes and related socio-economic impacts. In this talk we provide a first multiproxy-based real-world product for the Bayesian Hierarchical Modeling (BHM) formalism including spatial fields of European summer temperature covering the past 1200 years. We will demonstrate extreme past summers including 1540 that were likely more extreme than similar events in the instrumental period. Given the large spatial extent, the long duration and the intensity of the 1540 heat and drought, the return of such an event in the course of intensified global warming involves staggering losses, the dimension of which might be assessed by future economic analyses. Projected changes in the variability and extremes of European summer temperatures Julien Catiaux MétéoFrance, Toulouse, France [email protected] Beyond the mean warming, climate change may modify the temperature variability, with consequences on extreme events causing societal and environmental impacts. Here we focus on European summer temperatures and assess future changes in both the intra-seasonal variability and extreme events (heat waves), based on CMIP5 projections under three RCP scenarios. These projections suggest an increase in both day-to-day and diurnal variations of European summer temperatures, with a rather good model agreement on the sign, while uncertainties remain on the amplitude. For a given scenario, we show that the uncertainty is related to the dispersion in (i) the response of the North-Atlantic atmospheric dynamics and (ii) the amplitude of local thermodynamical responses such as the soil drying and the cloudiness decline. Then we investigate projected changes in heat waves, defined as periods of at least 3 consecutive days with extremely high daily maximum temperature affecting at least 30% of our domain of interest. The mean warming and, more marginally, the increase in temperature variability contribute to make heat waves more frequent, more intense, longer lasting and more extended spatially, but again with large uncertainties on the amplitude. In order to reduce such uncertainties, we explore links between simulated future changes and model skills in representing the presentday climate. For example, we show that the model-dependent degree of control of surface evapotranspiration by soil moisture appear as a helpful metrics to constrain future projections in both the mean and variability of European summer temperatures. 1 Riederalp-2015 Abstracts Volume Influence of soil moisture on summer air temperature Ján Hrvoľ, Martin Gera, et al. Comenius University, Bratislava, Slovakia [email protected] The purpose of this study is to identify the influence of reduced soil moisture in summer on the increase of the maximum mean air temperature with respect to the mean air temperature for the period 1951–2010. The summer 2003 is analyzed in this context. Computation of the maximum mean air temperature increase due to reduced soil moisture was processed for selected stations from Slovakia with different humid conditions. The mean monthly values of soil moisture were denoted from the water balance equation by the step-by-step approximation method. A physical model for the estimation of energy balance equation components (total radiation balance and its components, latent heat, sensible heat and heat flux in the soil) has been applied to active surface temperature computation. The average monthly air temperature and humidity, cloudiness, number of days with snow cover and precipitation were used as input parameters. It was found out that the o deficit of 1 cm soil moisture causes the increase of the mean summer temperature by about 0.35 C. It is supposed that this value depends on the net radiation sum because of atmosphere stability. An increase of the o mean summer air temperature due to soil moisture decrease about 0.4 C which is 22% of the whole mean o summer air temperature change (1.8 C) in the Slovakian most arid region was observed for the period 19512010. The impact of land-atmosphere interactions on the current and future temperature extremes over North America as simulated by the Canadian RCM (CRCM5) Gulilat Tefera Diro University of Quebec at Montreal, Canada [email protected] Land-atmosphere interactions play an important role in the climate system. In this study, we investigate how land-atmosphere coupling and interactions may affect future extreme temperature events, particularly the role of soil moisture in modulating the frequency and duration of hot spells, using the fifth generation of the Canadian Regional Climate Model (CRCM5), over North America. With this objective, CRCM5 simulations, driven by two different GCMs (MPI and CanESM2), are performed with and without land-atmosphere interactions for current (1981–2010) and future (2071–2100) climates, for RCPs 4.5 and 8.5. Analysis suggests that, for the summer season, associated with the soil moisture decreases in future climate, the soil moisture-temperature coupling regions, located over the US Great Plains in current climate, extend to cover a larger region, including large parts of central Canada. Results also indicate that land-atmosphere interactions contribute significantly to the projected changes in temperature extremes and it accounts for an increase of up to 10 hot-spell days per summer over central Canada. The increased strength of land-atmosphere coupling in these regions is reflected more in the changes to the variability of hot-spell characteristics than on projected changes to the mean characteristics, which implies important changes to rare severe temperature events. For parts of southern US, on the other hand, change in land-atmosphere interactions contributes to an increase in hot-spell 2 Riederalp-2015 Abstracts Volume days only under RCP4.5 scenario. This is due to the strong surface dryness under RCP8.5 scenario that leads the surface to have less evaporative fraction to affect the climate. Projected changes to hot/cold spell characteristics over Canada based on a Regional Climate Model ensemble Dae Il Jeong et al. University of Quebec at Montreal, Canada [email protected] Extreme hot/cold temperatures have significant impacts on human society and ecosystems, and therefore it is important to assess how these extreme events will evolve in a changing climate. The impact of climate change on summer hot temperature characteristics (i.e., hot days, hot spells, and heat waves) and winter cold temperature characteristics (i.e., cold nights, cold days, frost days, ice days, and cold spells), for 10 climatic regions covering Canada, based on 11 Regional Climate Model (RCM) simulations from the North American Regional Climate Change Assessment Program (NARCCAP), will be presented. The 11 NARCCAP simulations were produced with six RCMs driven by four Atmosphere-Ocean General Circulation Models (AOGCM), for the A2 emission scenario, for the current 1970–1999 and future 2040–2069 periods. The simulations suggest future increases in the number of hot days and hot spell events for the 10 climatic regions considered. Regionally, the Great Lakes, West Coast, Northern Plains, and Maritimes regions are found to be more affected due to increases in the frequency and severity of hot spells and/or heat wave characteristics, requiring more in depth studies for these regions to facilitate appropriate adaptation measures. The simulations, however, suggest future decreases in the frequency of cold extreme events and selected return levels of maximum cold spell durations over Canada. Densely populated southern and coastal Canadian regions, according to the projections, will experience large increases in the frequency of freeze-thaw events, and would require additional studies to provide appropriate adaptation measures. Increases of Tmax : Tmin ratios despite a slowdown in mean temperature increase in Europe Martin Beniston The University of Geneva, Switzerland [email protected] A study has been undertaken to analyze the behavior of record high and low values of temperature since the early 1950s for 30 locations spread across Europe. When establishing the ratios of the number of record Tmax to record Tmin values in each year, it is seen that there is a sharp increase in these ratios in the most recent decade. This seems to be an apparent paradox in view of the slow-down in atmospheric temperatures that has been observed since the early 2000s at both the hemispheric and European scales, but closer analysis suggests that the relationship between the record high:low ratios and mean annual temperatures is not linear but rather a 3 Riederalp-2015 Abstracts Volume square relationship. It is suggested that the record high to record low ratios in both the Mediterranean region and beyond 60° latitude north, observed in the most recent decade, may be related to an amplification of lowlevel atmospheric temperatures resulting from shorter snow seasons in the north and enhanced summer dryness in the south. Extreme events and their impacts as seen from documentary sources in the last 500 years Ricardo Garcia Herrera Universidad Complutense Madrid, Spain [email protected] Historical documentary sources are a valuable tool to analyze climate variability from a long term perspective. This presentation will be focused on the different possibilities to detect extremes as heat waves or droughts from this type of sources using documents from different archives in the world. Reconciling reconstructions and simulations of volcanic cooling Sébastien Guillet University of Bern, Switzerland [email protected] Explosive volcanic eruptions have repeatedly been linked to global climate and ecological change, with important implications on human history. Global cooling following such events has been simulated by climate models, and estimated from tree-ring based temperature reconstructions. However, climate simulations show a much larger short-term response to very large volcanic forcing than tree ring-based hemispheric temperature reconstructions. This mismatch has been attributed to the inability of tree-ring width proxies to record shortterm cooling induced by the largest eruptions, and to uncertainties in models and climate sensitivity to very strong volcanic forcing. Here, we present improved summer temperature reconstructions spanning the last 1500 years based on an unprecedented network of tree-ring series. A new volcanic forcing dataset is then used to simulate the largest volcanic events of the Common Era, in 1257 and 1815, accounting explicitly for self-limiting aerosol microphysical processes. For the first time, tree-ring proxies and climate simulations yield similar magnitudes for northern hemisphere, extra-tropical summer cooling over land induced by these eruptions, estimated at –1.2°C. Our results indicate the importance of a correct representation of climate sensitivity in models, and challenge both earlier temperature reconstructions and climate simulations performed with simplified reconstructions of very large volcanic forcings. 4 Riederalp-2015 Abstracts Volume Climate warming, permafrost melting and enhanced rock-fall activity Markus Stoffel The University of Geneva, Switzerland [email protected] Trees have been demonstrated repeatedly to be excellent recorders of rockfall activity on forested talus slopes, both in terms of their spatial and temporal activity and possible changes thereof. Rockfalls have also been described to depend, among others, on freeze-thaw cycles and the melting of winter ice in clefts, and that their temporal frequency and magnitude will likely be altered at higher elevations dominated by permafrost environments as a result of ongoing climatic changes. This paper focuses on rockfalls triggered from periglacial environments in Valais (Switzerland). It is anticipated that changes in permafrost conditions will affect the production of rockfall which would in turn be recorded in the vegetation growing on the steep slopes below cliffs. Based on the study of almost 800 time series of century-old Larix decidua trees, we demonstrate that rockfall activity – and therefore permafrost conditions – have been modified significantly at the study sites between the end of the Little Ice Age and today, and that such changes can be considered reflective of changing climatic conditions in general and of recent increases in temperatures in particular. A consistent picture of the hydroclimatic response to global warming from multiple indices: Models and observations Filippo Giorgi Abdus Salaam International Centre for Theoretical Physics, Trieste, Italy [email protected] We analyze trends of six daily precipitation-based and physically interconnected hydroclimatic indices in an ensemble of historical and 21st century climate projections under forcing from increasing greenhouse gas (GHG) concentrations (RCP8.5), along with gridded (land only) observations for the late decades of the 20th century. The indices include metrics of intensity (SDII) and extremes (R95) of precipitation, dry (DSL) and wet (WSL) spell length, the hydroclimatic intensity index HY-INT and a newly introduced index of precipitation area (PA). All the indices in both the 21st century and historical simulations provide a consistent picture of a predominant shift towards a hydroclimatic regime of more intense, shorter, less frequent and less widespread precipitation events in response to GHG-induced global warming. The trends are larger and more spatially consistent over tropical than extratropical regions, pointing to the importance of tropical convection in regulating this response. Observed trends in the indices analyzed are qualitatively and consistently in line with the simulated ones, at least at the global and full tropical scale, further supporting the robustness of the identified prevailing hydroclimatic responses. The HY-INT, PA and R95 indices show the most consistent response to global warming, and thus offer the most promising tools for formal hydroclimatic model validation and detection/attribution studies. The physical mechanism underlying this response are also discussed. 5 Riederalp-2015 Abstracts Volume The contributions of soil-moisture interactions to the future changes in the characteristics of daily precipitation in CMIP5 projections from the GLACE-CMIP5 experiment Wilhelm May Lund University, Sweden [email protected] The contributions of the projected changes in soil moisture to the overall future changes in the characteristics of daily precipitation at the end of the 21st century are quantified using the simulations from the GLACE-CMIP5 experiment. Five state-of-the-art global climate models have contributed to the GLACE-CMIP5 experiment, i.e., CESM, EC-EARTH, GDFL, IPSL and MPI-ESM. As these models show quite different geographical distributions of the future changes in soil moisture as well as different magnitudes, we do not consider ensemble mean values based on the corresponding simulations with these models but rather analyze the simulations from the different models separately. This allows for quantifying the contributions of the projected changes in soil moisture to climate change in the tropics for each climate model despite the different characteristics of the soil moisture changes themselves. The characteristics of daily precipitation are not only described by the frequency of wet days and the intensity of daily precipitation events, but also extremes of daily precipitation are considered, described via various percentiles of the intensity of daily precipitation events. In our study, the overall projected future changes in the characteristics of daily precipitation, which are partly related to changes in soil moisture, are directly compared to the corresponding changes that are not affected by any changes in soil moisture. The projected changes in the soil moisture content are found to give major contributions to the overall changes in the different aspects of daily precipitation, including extremes of daily precipitation events. More frequent droughts are pushing relict low-altitude Pinus uncinata stands into the greenhouse trap Christophe Corona Blaise Pascal University, Clermont-Ferrand, France [email protected] On the basis of a dendroecological analysis, we compared growth chronologies at two relict low altitude pine stands located in Paleorefugia with cold microclimates in the Chartreuse massif (French Alps). Two different detrending procedures are used to reveal high- and low-frequency wavelengths embedded in annually resolved ring width series. Growth responses of these P. uncinata stands to instrumental temperature and precipitation data are investigated by means of moving correlation analyses. Results show strongly divergent growth trends. La Plagne stand is located at the lower end of a N-NW exposed scree slope characterized by advective heat fluxes, with associated cold air flows blowing out of the ground in summertime, the presence of sporadic permafrost as well as ground overcooling in its lower parts. The negative effect of higher summer temperatures on tree growth is clearly absent here, since the gravitational discharge of cold air in the scree slope would maintain fresh and humid soil conditions. At Bresson stand, located on a small, south-exposed, poorly functional snow avalanche cone with very limited avalanche activity, a significant and rapid ring-width decline is observed and presumably related to (i) higher temperatures at the beginning of the 6 Riederalp-2015 Abstracts Volume vegetative period and to (ii) associated increases in water soil stress. The Bresson stand is shown here to react in a very direct and sensitive way to an increase of air temperatures and associated drought conditions since the 1980s, and may thus be among the first ecosystems of the Northern French Alps to be pushed into the greenhouse trap forever. Drought and hydroclimate variability in the western Americas Brian Luckman University of Western Ontario, London, Canada [email protected] In many parts of the western Americas cordillera rainfall or snowmelt runoff from the mountains is the primary source of water for adjacent semi-arid lowlands. Although there are continuing progressive temperature-related effects on the amount and duration of snowpack that may lead to gradual changes in hydrological regime, the principal causes of droughts are driven by changes in atmospheric circulation driven mainly by the Pacific Ocean. This paper will present examples from Canada, Mexico Chile and Argentina that that use tree-ring and hydrological records to demonstrate the nature of this variability and show how an understanding of long and short term variability is critical to the future management of water resources. Year to year variability in mid-low latitudes is dominated by ENSO e.g. average flows of the Rio Nazas in Mexico (ca 26°N) in El Niño years average 2-3 times those in La Niña years. However, significant low frequency variability also exists indicating there are other controls that result in decadal scale droughts in this record. At higher latitudes the low frequency variability is a stronger influence where changing large scale pressure patterns set up periodic or quasi-periodic patterns of varying duration and spatial extent (PDO, AAO, NAO, PNA etc.). Twentieth century streamflow records in the Central Andes of Chile and Argentina (30-37°S) show regime shifts with a 31% decrease (28% increase) in mean flows that are synchronous with the 1946-7 (1976-7) shifts of the PDO. The paper will explore the implications of these changes for future water management in the adjacent lowlands. Critically, these studies demonstrate the nature and range of hydroclimatic variability that must be accommodated in meeting sustainable future water management needs in these regions. Assessing small scale heavy precipitation from stability indices in RCMs David Leidinger University of Natural Resources and Life Sciences (BOKU), Vienna, Austria [email protected] To assess the possible change of strong convective cells (thunder storms), the analyses of the precipitation from regional climate models (RCM) is not sufficient due to the limitations from the still coarse resolution and the precipitation parameterization itself. The analyses and interpretation of the vertical stability of the atmosphere in the RCM fields might give more robust results and additional insights. A possible indicator for these analyses is 7 Riederalp-2015 Abstracts Volume the Showalter index. This indicator can be calculated by standard output from regional climate models. More complex indicators like “CAPE” would need more vertical layers for calculation as available at the EURO-CORDEX database. To derive the relations between local convective cells and Showalter index values, the Showalter index will be calculated from a high resolution ( 10x10 km) reanalysis dataset. Showalter index values will be compared with local observations (RADAR and precipitation) and relevant thresholds of Showalter index values will be derived. To assess the climate change signal, the Showalter index will be calculated for selected RCMs from the temperature and dew-point temperature in 850 hPa and 500 hPa. The comparison of the spatial distribution and statistical measures from Showalter values within the reanalyses model run and the regional climate models will give information about the reliability of this indicator from the climate models. The temporal development of the Showalter index values above the derived thresholds within the 21st century will give a climate change signal for very strong thunderstorms. Shifts in extreme events in the Hindu-Kush-Himalaya (HKH) region Christian Siderius The University of Wageningen, The Netherlands [email protected] The Hindu Kush Himalayan (HKH) region provides water resources and other ecosystem services to more than 1.5 billion people in its mountains and floodplains. Socio-economic changes in combination with climate change impacts will significantly affect their livelihoods. Over the past years, scientific consensus has been building on the general pattern of climate change in the HKH region. What is still very uncertain is how a combination of increasing temperatures and changing precipitation patterns will lead to shifts in the timing of precipitation and runoff and in the frequency of extreme weather events. Flooding already appears to affect the Ganges basin more frequently. Extreme snowfall occurs more often during the trekking season. Indications of change in the frequency of droughts are ambiguous. Translation of how more local and seasonal, time-specific shifts will impact people in the mountains and plains during critical moments (e.g. water shortage during sowing time), and how to adapt to these shifts, is still largely unexplored territory. To address priority adaptation issues in Pakistan, India, Bangladesh, and Nepal, a new research project called HI-AWARE is specifically looking into the time dimension of adaptation and developing robust evidence for enhancing the adaptive capacities and climate resilience of the poorest and most vulnerable people. The project adopts a comparative and cross-scalar approach, with research and pilot adaptation intervention sites representing a range of climates, hydrological conditions and socioeconomic contexts. 8 Riederalp-2015 Abstracts Volume Rainfall and snow-melt triggered glacial lake outbursts: a systematic analysis of the Kedarnath (Uttarakhand, India), June 2013 disaster Simon Allen The Universities of Geneva and Zurich, Switzerland [email protected] Heavy rainfall in early June 2013 triggered flash flooding and landslides throughout the Indian Himalayan state of Uttarakhand, killing more than 6000 people, of which the vast majority of fatalities and destruction resulted directly from a lake outburst and debris flow disaster originating from above the village of Kedarnath on June 16 and 17. We provide a systematic analysis of the contributing factors leading to the Kedarnath disaster, both in terms of hydro-meteorological triggering and topographic predisposition. Topographic characteristics of the lake watershed above Kedarnath are compared with other glacial lakes across the northwestern Himalayan states of Uttarakhand and Himachal Pradesh, and implications for glacier lake outburst hazard assessment in a changing climate are discussed. Early onset of heavy monsoon rainfall (390 mm, June 10 – 17) immediately following a prolonged four week period of unusually rapid snow cover depletion is considered the crucial hydro-meteorological factor, resulting in slope saturation and significant runoff into the small seasonal glacial lake. Between mid-May and mid-June 2013, snow covered area above Kedarnath decreased by around 50%. The unusual situation of the lake being dammed in a steep, unstable paraglacial environment, but fed entirely from snow-melt and rainfall within a fluvial dominated watershed is important in the context of this disaster. A simple scheme enabling large-scale st recognition of such an unfavorable topographic setting is introduced. In view of projected 21 century changes in monsoon timing and extreme precipitation in South Asia, improved emphasis should be given to potential hydrometeorological triggering of lake outburst and debris flow disasters in the Himalayas. Extreme hydro-meteorological events – A case study of two successive flash floods in the Central Himalayas Manohar Arora National Institute of Hydrology, Roorkee, India [email protected] The entire Himalayan region is vulnerable to rain-induced (torrential rainfall) hazards in the form of flash floods, cloudbursts or glacial lake outburst flood. Torrential rains in 2013 have triggered devastating flash floods in the Mandakini, Saraswati, Madhu and Dudh Ganga catchments, whereas the breaching of Chorabari Lake caused excessive flood flows in the Mandakini (Kedarnath) Valley. The main reason for the occurrence of these flash floods was continuous rainfall between June 15 and 16, 2013 (325mm), which also enhanced snow and ice melt in the region. There were two major events in quick succession. A very high peak discharge has been recorded just before the flood event which occurred in the evening of 16 June 2013 which was estimated to be three to 9 Riederalp-2015 Abstracts Volume four times larger than normal June discharge. The second devastating event occurred in the morning of 17 June 2013 and after the collapse of moraine-dammed Chorabari Lake, which in turn released a large volume of water that caused another flash flood in the Kedarnath town leading to heavy devastation downstream. The hydro-meteorological and discharge data for 14 to 18 June 2013 – collected at an observatory near the snout of Gangotri glacier – illustrates that total rainfall during this 5-day storm was 178 mm. In the past, this area normally received much less rainfall and the maximum June rainfall during previous years hardly exceeded 93 mm. The sudden increase of water discharge in the river resulted in excessive downstream flooding. Flows at the gauging site peaked at 163 m3 s−1 on 16 June 2013. The paper also provides insights into preventive measures that may help in preparing a roadmap towards sustainable development in the region. Understanding gained from the Kedarnath disaster should therefore guide further hazard and risk studies accordingly. Understanding extreme flood events in ungauged mountain streams and their links to climate change Juan Antonio Ballesteros Cánovas The Universities of Geneva and Bern, Switzerland [email protected] Floods worldwide may be conditioned by large-scale atmospheric circulation anomalies, which some authors have recently related to climate changes. Such a hypothesis has, for instance, been presented in the case of the extensive floods in (northern) Europe during the winter 2013/14. However, the lacks of long flood records have prevented the drawing of more robust conclusions in this regard. In fact, general scientific consensus exists on the need to extend existing flood records through the use of different proxies. Through the presentation of several study cases conducted in Europe during last years, we provide examples on how paleohydrologic records can be obtained from living trees (dendrogeomorphology) to complement the systematic flood record in mountain environments and to improve our understanding about flood-climate linkages. We illustrate how extreme flash floods have been dated and their peak discharge reconstructed using hydraulic models along different mountain ranges in Spain and Slovakia; allowing to describe intense changes in fluvial geomorphology and the specific triggers of individual floods. On the other hand, in different catchment at the Polish Tatras, this methodology has allowed to define average flash flood frequencies and to identify periods that were “rich” and “poor” in flash floods during the last three centuries, as well as their seasonality, rainfall triggers and climate conditions of these events. The temporal coincidence of intense events in specific years in these and other geographic regions of the Northern Hemisphere allows a better understanding of climatic forcing/controls of such events at large scales and over longer timescales than before. 10 Riederalp-2015 Abstracts Volume Use of historical sources in a study of the hydrometeorological extremes in the Danube River Basin Marian Melo et al. Comenius University, Bratislava, Slovakia [email protected] When studying and reviewing the flood regime at present, it is necessary to pay due attention to documentary data in archives. In these historical materials, the courses, causes and impacts of various floods are described. It is still possible to find out new information on flood history over our territory, enabling us to better evaluate the flood peak exceedance probabilities (T- year flood peaks) for future scenarios. Measured meteorological and hydrological data series are temporally limited. Instrumental data can be complemented by documentary data from historical sources in different archives. This historical information can be related to extreme weather and climate events in the past (floods, droughts, heat, cold, wind storms, etc.). Most of the information has its origin in official letters, chronicles, newspaper articles, flood marks, books, maps and photos. In this contribution we bring information about hydrometeorological extremes in the Danube River Basin. We focus on the history of floods of the Danube River and especially on the catastrophic flood in year 1895. We clarify meteorological causes of this flood. Records from the contemporary local press and other analysed sources show the relatively large territorial impact of the floods in March and April 1895, which affected not only the Danube and its tributaries, but also some neighboring basins (Elbe, Dniester, Bug). Catastrophic consequences of this flood were especially reported from the lower parts of the Danube River (from its confluence with the Drava River up to the mouth of the Black Sea) and the tributaries of the Tisza and Sava rivers. Increasing of severe hydrological events in the Po basin under global warming Barbara Tomassetti University of l’Aquila, Italy [email protected] It has been long recognized as the global changes are leading to increase the occurrence of severe weather events and, in the last few years, many critical hydrological situations have actually been observed in many areas of the world. North Italy seems to be a most vulnerable region since it has been interested by many floods in the recent years, especially during fall season. In these work we used a distributed Hydrological Model, forced with a Regional Climate Model, to investigate possible trends of expects flood events in the upper Po basin and surrounding areas. In order to evaluate such trends we used two different alarm indexes that have been tested and operationally used for flood alarm mapping; the analyses are carried out for the years 1960-2050 and the main goal is to verify if a positive trend in the occurrence of flood events is actually to be expected and what are the segments of drainage network that are most affected by such trend. A first alarm index is calculated, at hourly time step, as a function of predicted discharge; for each elementary cell of the simulated domain, we 11 Riederalp-2015 Abstracts Volume consider a situation of flood alarm when the predicted discharge overcome a threshold value estimated for each single grid point. A second more empirical index is calculated as a function of the predicted precipitation in the upper basin. Emphasis is also given the detailed description of the proposed innovative approach. Scenarios of changes in local precipitation extremes for the Netherlands Geert Lenderink KNMI, De Bilt, The Netherlands [email protected] Local precipitation extremes are important for many applications regarding climate change adaptation, for instance concerning urban flood management, design of infrastructure and soil erosion. In a warming climate these type of extremes are generally expected to increase due to projected increases in moisture content of the atmosphere. The latter can be measured directly by the dew point temperature, where (near the surface) each degree rise represents an increase of 6-7 % in atmospheric moisture according to the Clausius-Clapeyron relation (hereafter CC relation). However, the atmospheric processes, turbulence and cloud physics and dynamics, leading to local extreme precipitation are barely (or not) resolved in present-day climate models and therefore we cannot fully rely on the output of climate models concerning these type of extremes. Here, I will therefore discuss other lines of evidence. First, observations of hourly precipitation extremes for the Netherlands show an increase close to two times the CC relation (hereafter 2CC) derived from short term variability. For 10 min precipitation a 2CC behavior is even obtained over an almost 20-degree dew point temperature range. Second, this 2CC relation also explains the long term trends of hourly extremes in The Netherlands very well. Third, short integrations with an atmospheric mesoscale model, in which the largest motions in a convective cloud are resolved, show a dependency on dew point temperature slightly below 2CC. The background and generality of these findings will be discussed, and this knowledge will be applied to generate climate scenarios of local precipitation extremes for The Netherlands. Drought frequency in the last three centuries in Moscow region (Russia) from pine and oak ring width chronologies Olga Solomina and Vladimir Matskovsky Russian Academy of Sciences, Geography/Glaciology, Moscow, Russian Federation [email protected] We present new tree-ring network of 14 ring width chronologies of pine (Pinus silvestris) and oak (Querqus robur) in the Moscow region (55-60N, 35-45E). The chronologies are from 120 to 300 years long. The highest correlation of the ring width of both species for most chronologies is found with the PDSI and CPC, i.e. our chronologies are potentially useful for the drought reconstructions. Most common growth suppression for the period from 2014 to 1731 are recorded in this region in 2010-2011, 2002-2003, 1964-1965, 1956, 1921, 18971898, 1890-1891, 1888-1889, 1845, 1830, 1797. Most of them coincide for oak and pine. The heat wave, which 12 Riederalp-2015 Abstracts Volume occurred in July and August 2010 in Moscow region, is recorded in seven chronologies in Kostroma, Yaroslavl’, Moscow and Kaluga regions in 2010 and 2011, however in the southernmost oak chronology (Tula region) both years were regular in terms of ring width. Three previous droughts (2003, 1939, and 1936 are recorded even more often in the ring width chronologies than the 2010 event). By the amplitude of growth suppression the years 1964, 1956, 1939, 1936, 1921, 1897, 1891, 1845, 1797, 1787, 1767 exceed those of 2010 and 2011. The modeling results show that the heat wave of 2010 does not yet exceeded the natural variability of the last 250300 years, however by its amplitude it is at the edge of the probability of natural droughts (Dole et al., 2011). How extreme can storms become? David B. Stephenson The University of Exeter, United Kingdom [email protected] A flexible spatio-temporal statistical model is developed to analyse extreme extra-tropical cyclones over the Atlantic and Europe tracked in 6-hourly re-analyses from 1979–2009. Spatial variation in the extremal properties of the cyclones is captured using a 150 cell spatial regularisation, with latitude as a covariate, and spatial random effects. The North Atlantic Oscillation (NAO) is also used as a covariate and is found to have a significant effect on intensifying extremal storm behaviour, especially over Northern Europe and the Iberian peninsula. Estimates of lower bounds on minimum sea-level pressure are typically 10–50 hPa below the minimum values observed for historical storms with largest differences occurring when the NAO index is positive. Dynamical downscaling of historical windstorms for modeling wind hazard in Switzerland Peter Stucki University of Bern, Switzerland [email protected] Windstorms represent a major natural hazard with potential damage to buildings or forests. Impacts from extreme windstorms are substantially dependent on peak wind speeds. For modeling wind hazard in Switzerland, high-resolution wind observations are available since around 1980. Atmospheric reanalyses mostly cover recent decades only, and hence a relatively small number of rare, i.e., extreme events. To compensate, we use the Twentieth Century Reanalysis (20CR) dataset, which reaches back to 1871, as boundary conditions for dynamical downscaling of wind fields to a grid size of 3 km. The Weather and Research Forecasting model (WRF) is applied to 83 historical winter storms which are retrieved from a catalog of highimpact windstorms in Switzerland since the mid-19th century. The modeling chain is illustrated for a high-impact 13 Riederalp-2015 Abstracts Volume foehn storm that occurred in the Swiss Alps on 15 February 1925. The WRF simulations show realistic wind fields and dynamics over complex terrain, consistent with traditional meteorological concepts and wind information. The 20CR ensemble mean is a suitable representative of the full information from 56 ensemble members. Model limitations are seen in sub-grid wind flow dynamics and the wind gust parameterizations, among others. The method may break new ground for a range of research and business applications which require highresolution, consistent and long-term data coverage. First applications include the production of new maps of wind hazard in Switzerland and the modeling of economic losses from windstorm hazard at Swiss municipality level. Severe rain, hail, lighting and the number 42 Bodo Ahrens Goethe University, Frankfurt am Main, Germany [email protected] This presentation sheds light on the influence of the land surface (incl. orography) and air mass characteristics on atmospheric convection as observed with radar, lightning, and satellite data over the hilly region of Thuringia/Germany. A climatological relevant number of severe events is hindcast with convection permitting simulations (CPSs) applying the regional climate model COSMO-CLM driven by re-analysis data and investigated. Climate change of convective hazardness is quantified by using appropriate indices calculated from simulations of two global climate simulations and by using analyses of CPS of several hundred convective events. The results show that the hazardness patterns and intensities clearly depend on landscape and weather type and change with climate change with amplified changes if CPSs are used because of realized feedbacks. Climate extremes in an ensemble of CORDEX regional climate scenarios for Europe Erik Kjellström Swedish Meteorological and Hydrological Institute, Norrköping, Sweden [email protected] In this study we investigate possible changes in temperature, precipitation and wind extremes on a regional scale over Europe from 1961 to 2100. We use data from two ensembles of regional climate simulations over the Europe-CORDEX domain at 0.11º and 0.44º resolution respectively. The Rossby Centre regional climate model RCA4 is used with boundary conditions from nine coupled atmosphere ocean general circulation models (AOGCMs) from the CMIP5 project (CanESM2, CNRM-CM5, HadGEM2-ES, IPSL-CM5A-MR, NorESM1-M, ECEARTH, MIROC5, GFDL-ESM2M and MPI-ESM-LR). RCA4 is operated at 0.44º resolution (c. 50 km grid spacing) for all nine AOGCMs and at 0.11º resolution (c. 12.5 km) for a subset of five. Two forcing scenarios are considered, RCP 4.5 and 8.5. The experimental setup allows us to illustrate how uncertainties in future climate change are 14 Riederalp-2015 Abstracts Volume related to forcing scenario and to forcing AOGCM at different time periods. Further, we investigate the benefit of higher horizontal resolution in RCA4 by comparing the results at 50 and 12.5 km. In addition to characterizing future changes we compare model results to climate extremes as estimated from the E-OBS observations and from a new regional reanalysis product from the FP7 project EURO4M. Coastal hazards and Mediterranean storms Piero Lionello University of Salento and CMCC, Italy [email protected] A well-defined and intense branch of the mid-latitude storm track crosses the Mediterranean region and produces severe weather events with storm surges, high ocean waves and intense precipitation along its coastline. Most of these extreme events are associated with the presence of cyclones, though the intensity of their effects varies greatly depending on characteristics of the cyclones, such as their position, intensity, speed, extension. There is an emerging evidence that a progressive attenuation of the Mediterranean storms will occur in the future, leading to lower surges and waves than presently (and less precipitation, as well). However, the level of hazard that is posed at the coast depends also on other factors, mainly on the increase of mean sea level, so that accounting for its evolution is required for reaching a comprehensive conclusion on future hazards. This requires to consider regional (steric) effects and remote causes (such as mass addition across the Gibraltar strait). Accounting for these processes shows that increase of sea level is likely to increase the intensity of marine hazards, in spite of the marine storms becoming milder than now in the future. Robust Forced Signals and Irreducible Uncertainties in Projections of Extremes Erich Fischer ETH-Zurich, Switzerland [email protected] Decision makers express a strong need to shift the focus of climate projections from changes at global scale to changes at regional to local scale, from the end of the century to the coming decades, from changes multidecadal mean temperatures to changes in extreme events. This new focus of climate projections implies an increasing contribution of internal variability to projection uncertainties. Understanding and quantifying the role of internal variability is vital to identify the limits of predictability – the irreducible uncertainty in multi-decadal projections – and the limits of model evaluation and bias correction. Using different large initial condition ensembles, we demonstrate that models agree remarkably well on the forced signal of temperature and heavy precipitation extremes, the pattern of change in the absence of internal variability. The disagreement between individual model simulations on local to regional changes in extremes primarily arises from internal variability. Thus, in the coming 3-5 decades trends towards more intense hot and 15 Riederalp-2015 Abstracts Volume less intense cold extremes may be masked or even reversed in some places even if greenhouse-gas emissions rapidly increase. Likewise, despite a trend to more intense precipitation, opposite trends of multiple decades cannot be excluded over most land points. Despite large irreducible uncertainties at local scale, in an aggregated spatial probability perspective projections are again remarkably consistent already for the coming decades. Our findings demonstrate that within all the complexity of non-linear processes controlling temperature and heavy precipitation extremes, a remarkably simple first-order pattern emerges: as global temperatures increase, the forced hot extremes and heavy precipitation intensification is widespread over most of the land region and consistency across models for these changes is high in particular over Eurasia and North America. Evaluating simulated precipitation extremes Andrea Toreti European Commission, Joint Research Centre, Ispra, Italy [email protected] A novel nonparametric approach to evaluate precipitation extremes simulated by climate models is proposed and applied to high horizontal resolution CMIP5 simulations over the Euro-Mediterranean region. The method is used to perform a model inter-comparison, to compare historical runs with gridded observations (E-OBS); to evaluate future projections under the high emission scenario RCP8.5. Results support the existence of a scaling relationship of the conditional mean of extremes among models and w.r.t. the observations both in winter and autumn. However, rescaled tails of simulated precipitation show a significant underestimation (overestimation) in the northern-central (southern) part of the domain when compared with observations. Concerning the st projections for the mid-21 century (2020-2059), almost all models agree on an intensification of extremes linked to an increase of the conditional mean but they do not show any significant change in the tail behaviour. At the end of the century (2060-2099), the same tendency of the conditional mean is confirmed, but a lack of model agreement (implying a higher uncertainty) prevents to draw conclusions on the changes affecting the upper tails. Heat waves over Central Europe in ENSEMBLES and CORDEX RCMs: past biases and future uncertainties Ondřej Lhotka Global Change Research Centre, Brno, Czech Republic [email protected] We evaluate simulation of Central European heat waves in the recent climate and projected changes for the 21st century in an ensemble of regional climate model (RCM) simulations from the ENSEMBLES and CORDEX projects. Observed data are represented by the E-OBS gridded dataset. Heat waves are defined based on excesses above the 90th percentile of summer daily maximum temperature (T max), and their temporal as well as spatial characteristics are considered. In historical runs, RCMs tend to simulate more heat waves than observed 16 Riederalp-2015 Abstracts Volume (although the percentiles are calculated for each RCM in order to remove Tmax biases), which is due to overestimated clustering tendency of days with high temperature in the RCMs. The simulated heat waves have also too pronounced temperature peaks. We examine also driving mechanisms for major heat waves over Central Europe in the past, especially the most severe 1994 heat wave, and show that its reproduction in the RCMs is closely linked to simulated precipitation and soil moisture. Projected changes of the heat wave characteristics are analysed for two time slices corresponding to near (2020–2049) and far (2070–2099) future. Although the RCMs generally agree on the increased heat wave severity, the multi-model spread is large, indicating considerable uncertainty in climate change scenarios of Central European heat waves. Better understanding the RCMs’ biases and uncertainties related to such factors as emission scenarios, driving global models, spatial resolution and natural variability, will be essential for impact studies as well as design of suitable adaptation and mitigation strategies. Impact of daily temperature homogenization on cold extreme indices in Switzerland Renate Auchmann University of Bern, Switzerland [email protected] Many applications in climate science require high-quality, long-term data at a high temporal resolution. However, such records are often affected by artificial breaks, so-called inhomogeneities, due to, for instance, station reclocations or changes in instrumentation. Homogeneous daily data are required for studying extremes and changes thereof, especially since inhomogeneities can alter the whole distribution of a series; both the mean and the tails can be affected. Analysis of daily data has come into focus continuously in the past decades with the growing attention of possibly changing climate extremes in the view of climate change. The challenging task of homogenizing daily and sub-daily data has only been partially addressed in recent years. Therefore, the number of available datasets providing homogeneous daily and sub-daily series is still small compared to the volume of monthly or annual data. For studying changes in the extremes it is crucial to use homogenous data otherwise wrong conclusions can be made when estimating e.g. trends in extremes. In this paper all daily and sub-daily temperature series from Switzerland are being homogenized. Switzerland is an interesting study site for homogenization purposes because it offers a dense network of stations with rather long series (up to 250 years) but it also has a very complex terrain (Alps). The correction method used (HOMAD) accounts for the whole distribution of a temperature series. We present cold indices/trends in Switzerland (using minimum temperatures) from the raw and homogenized series and assess the impact of homogenization on the results. 17 Riederalp-2015 Abstracts Volume Hierarchical Bayesian space-time modelling to infer climatic trends from extreme events in mountainous environments Nicolas Eckert IRSTEA, Saint-Martin-d’Hères, France [email protected] Recently, Hierarchical Bayesian modelling has seen growing interest for processing large environmental data sets, for instance gridded climate data. This framework is also particularly well suited for inferring a climatic signal from a set of partially correlated series of extreme events such as debris flows or avalanches. The nonlinear nature of their response to climate covariates can be acknowledged at the latent variable level. Furthermore, the signal common to a large number of series can be more confidently linked to regional climate change than the one extracted from a single observation record. Finally, significant spatio-temporal patterns such as change points can be separated from “random” annual fluctuations, with the different sources of uncertainty treated rigorously, e.g. taking into account missing values and the uncertainty regarding annual estimates when inferring the temporal patterns of interest. The objective of this talk is to illustrate these statements using complementary examples illustrating different aspects of the approach (covariates, model structures, signal decomposition and cross validation, etc.). We will show that, in addition to providing concordant insight about recent climate change in the French Alps, this framework may be potentially usable for many other applications, even if major statistical and applied challenges still remain. Modelling Climate Change and Socioeconomic Pathways in the Ganges and Brahmaputra River Systems Paul Whitehead University of Oxford, United Kingdom [email protected] A semi-distributed flow and water quality model (INCA) has been set up for the whole of the Ganges and Brahmaputra River Systems from the High Himalayas, through the middle hills, down to the plains of India and Bangladesh. The INCA model simulates daily flows, sediments and nutrients (nitrogen, ammonia, total and soluble phosphorus) and has been applied as part of the ESPA Deltas Project (see www.espadelta.net) The rivers transport large fluxes of water, sediments and nutrients and are driven by climate extremes and socioeconomic change. Future climate change has been assessed using the daily precipitation and temperature predictions from the UK Met Office GCM model linked to a regionally coupled model of South East Asia, covering India, Nepal, China, Tibet, Bhutan and Bangladesh. Daily simulated modelling results indicate a shift in the monsoon season with increased wet season flows and decreased low flows, exacerbating problems of floods and drought. The altered flows and temperature regimes also alter nutrient fluxes which will impact river and delta ecosystems. Socio-economic changes have also been assessed using INCA by investigating changes in future population, land use (eg agriculture, urban and forest conditions), atmospheric deposition of nutrients and also point source pollution from expanding cities, industry and intensive agriculture. Also, the model is currently being used to assess alternative adaptation and management strategies for the catchments with advice provided to the 18 Riederalp-2015 Abstracts Volume Governments of India and Bangladesh. Finally INCA is a fast and flexibly model which allows for stakeholder engagement and for rapid assessment of adaptation and mitigation strategies. Extreme floods in mountain valleys – towards a physically-based warning system Benjamin Brock Northumbria University, Newcastle, United Kingdom [email protected] Recent decades have seen an increase in the frequency of damaging and fatal floods in the Alps, associated with intense precipitation events. In mountain areas, elevation, steep slopes and basin morphology can enhance precipitation and concentrate runoff, generating highly peaked ‘flash’ floods which are difficult to predict and prepare for. In glacierised basins, convective storms occurring during hot weather can generate severe floods through the combination of intense precipitation and high snow and ice melt runoff. Mountain basins present particular challenges to hydrological models due to complex topography, varied land surface types, temporal changes in snow cover and paucity of instrumental data. Substantial progress has been made in addressing these issues through ongoing research. Runoff in mountain rivers can now be modelled with a high degree of accuracy due to advances in physically-based hydrological modelling and DEM generation from remotely sensed data. If combined with suitable input data, either from model forecasts or real time data, the current generation of models have the potential to provide advanced warning of dangerous floods and to assess how frequency and intensity of flooding my change under future climatic scenarios. This contribution will i) examine flood hydrographs from high elevation mountain streams and in particular the characteristic of an extremely steep ‘rising limb’ during extreme flood events; ii) assess the potential of state-ofthe-art hydrological models to simulate extreme flood events and how they could be used as an operational flood prediction tool and to evaluate long term flood risk under a changing climate. Adaptation to river floods, today and tomorrow Zbiegniew Kundzewicz Polish Academy of Sciences, Poznan, Poland [email protected] Despite all the costly investments in river flood defences, the costs of flood damages keep increasing, at various spatial scales. Discussion of flood risk management strategies, such as flood prevention, flood defence, flood mitigation, flood preparation, and flood recovery is offered, as well as justification of the need for diversification of strategies. Implementation of strategies depend on flood risk governance arrangements, whose essential elements are: actors, discourses, resources, and rules. Flood risk reduction is an objective of two activity areas – disaster risk management and climate change adaptation (despite all the uncertainty in climatic projections 19 Riederalp-2015 Abstracts Volume relevant to floods). An approach integrating the two areas should be seen in the overarching perspective of sustainable development. Implementation of the Floods Directive of the European Union is also discussed. Analysis of extreme climatological events in the Carpathian region for regional adaptation planning Judit Bartholy and Rita Pongracz Eötvös Lorand University, Budapest, Hungary [email protected] Various socio-economic sectors are considerably affected by different types of climatological and meteorological extremes. For instance, the lack of precipitation for extended period and coincidental intense heat wave often lead to severe drought events, which cause quite high negative impact on agricultural production. In order to avoid or at least reduce the effects of these climate-related hazards, national and local communities need to develop and use regional adaptation strategies (e.g., the Hungarian Parliament accepted National Climate Strategy in 2008, which is currently under revision extended by a national adaptation strategy and a decarbonization plan). For this purpose, results of global climate model (GCM) simulations must be downscaled to regional and local scales, hence better serving end-users’ needs. Our research group focuses on providing regional scale information using (i) a multi-model approach, which consists of 11 regional climate model (RCM) simulations from the ENSEMBLES project with 25 km horizontal resolution; (ii) our RCM simulations with PRECIS and RegCM models completed specifically for the Central European domain with 25 km and 10 km horizontal resolution. Our analysis considers both the previous SRES emission scenarios and the new RCP scenarios. According to our results, the Carpathian region is projected to become warmer, and also, drier in summer, which highlight the necessity of appropriate planning, especially from agricultural and energy point of view. Windstorm loss models, state of the art, challenges and future directions Paul Della Marta Partner Reinsurance Company, Zurich, Switzerland [email protected] We present an overview of the windstorm catastrophe loss models developed at PartnerRe, the data and methodologies they are based on and highlight areas where engagement with the scientific community is needed to help bring their state-of-the-art forward. Our European windstorm model uses around 140 7km th resolution NWP based historical windstorm footprints to calibrate a multi-model ensemble of 20 century and future scenario RCM. The calibration method relies on downscaling and a statistical correction to be compatible with the historical event set. Issues arise from the use of multiple RCMs whose windstorm climatologies are different. The Atlantic Hurricane model utilizes reanalysis data combined with a beta and advection model. This method has advantages over traditional methods which use only the historical track information since it allows hypothetical storms stacks to be driven by the dynamics within the re-analysis rather than observed statistics 20 Riederalp-2015 Abstracts Volume alone. Uncertainties and biases in steering wind obtain from re-analysis products in low latitudes combined with the method of removal of vortices present challenges. The U.S. tornado model uses three different methods to produce stochastic wind fields. The NOAA severe storms database is often incomplete and has limitations which require many statistical based corrections or statistical modeling to make the data suitable as the basis of simulating their stochastic behavior. The three methods can be summarized as historical perturbation, resampling from space-time probability densities and principal component based simulation. The small spatial scale of such events present challenges for producing a stochastic event set with sufficient convergence to be able to assess risk at a single location. Attribution of loss and damage to climate change and implications for climate policy Christian Huggel et al. University of Zurich, Switzerland [email protected] Disasters related to extreme weather events have caused loss and damage on the order of up to tens of billions US dollars for single events over the past years. Recent disasters fueled the debate about whether and to what extent these events are related to climate change. In international climate policy negotiations under the UNFCCC the discussions on loss and damage have gained significant traction during the past negotiation rounds. At COP 19 the Warsaw International Mechanism for Loss and Damage (WIM) was created as an institutional arrangement to address this issue. Thereby, loss and damage (L&D) is typically defined as the residual damage and loss that occur beyond mitigation and adaptation efforts. This implies that effective mitigation and adaptation policy can substantially reduce L&D. However, the exact definition and the framing of L&D under the UNFCCC is still unclear, with some developing countries arguing that L&D should form a separate mechanism, outside the adaptation framework. Related to these questions are claims about compensation of L&D. Even though developed countries have so far refused negotiations about compensation regimes, some scholars and experts argue that compensation will need to be addressed in the frame of the upcoming new climate regime, which would likely imply discussions about causation of L&D. However, the exact type of scientific evidence for such a new mechanism is unclear. Here we analyze different types of scientific evidence and how it can inform climate policy and specifically L&D discussions, including the detection and attribution of L&D to climate change. We draw on progress following from the IPCC 5th Assessment Report as well as several case studies around the world that include both extreme events and effects of gradual climate change. 21 Riederalp-2015 Abstracts Volume 1 Riederalp-2015: List of participants Family Name First Name Affiliation e-mail address AHRENS Bodo Goethe University, Frankfurt am [email protected] Main, Germany www.climtropy.de ALLEN Simon Universities of Geneva and Zurich, [email protected] Switzerland - ARORA Manohar NIH, Roorkee, India http://www.nih.ernet.in/manpower.html [email protected] Institute of Geography and Oeschger Center for Climate [email protected] Change Research, University of Bern, Switzerland Universities of Geneva and Bern, [email protected] Switzerland Website AUCHMANN Renate - BALLESTEROS Juan Antonio BARTHOLY Judit Eotvos Lorand University, Budapest, Hungary [email protected] - BENISTON Martin Univerty of Geneva, Switzerland [email protected] www.unige.ch/climate BROCK Ben Northumbria University,Newcastle, [email protected] United Kingdom https://www.northumbria.ac.uk/about-us/our-staff/b/ benjamin-brock/ CATTIAUX Julien CNRM-GAME, CNRS/MétéoFrance, Toulouse, France [email protected] http://www.cnrm-game.fr/spip.php?article629 CORONA Christophe Université Grenoble-Alpes, StMartin-d'Hères, France [email protected] http://geolab.univ-bpclermont.fr/ DELLA MARTA Paul Partner Reinsurance Company, Zurich, Switzerland [email protected] www.pauldellamarta.com DIRO Gulilat Tefera University of Quebec at Montreal, Canada [email protected] - http://www.dendrolab.ch/en/jab.php Riederalp-2015 Abstracts Volume 2 ECKERT Nicolas Irstea, France [email protected] http://www.irstea.fr/en/eckert FISCHER Erich ETH Zurich, Switzerland [email protected] www.iac.ethz.ch/people/fischer/ GARCIAHERRERA Ricardo Universidad Complutense, Madrid, [email protected] Spain GERA Martin GIORGI Filippo GUILLET Sébastien University of Bern, Switzerland [email protected] www.dendrolab.ch HUGGEL Christian University of Zurich, Switzerland [email protected] http://www.geo.uzh.ch/~chuggel/ http://eclim-research.ch/ JEONG Dae Il [email protected] http://www.escer.uqam.ca/jeong_EN.html KJELLSTROEM Erik [email protected] - KUNDZEWICZ Zbigniew [email protected] http://nimbus.elte.hu LEIDINGER David [email protected] http://www.wau.boku.ac.at/met/forschungsthemen/ klima-und-klimafolgen/ LENDERINK Geert LHOTKA Ondřej LIONELLO Piero Univ. Salento and CMCC, Italy [email protected] LUCKMAN Brian Henry University of Western Ontario , London, Canada [email protected] Comenius University in Bratislava, [email protected] Slovakia Abdus Salam Intl Centre for Theoretical [email protected] Physics (ICTP), Trieste, Italy University of Quebec at Montreal, Canada Swedish Meteorological and Hydrological Institute, Norrköping, Sweden Polish Academy of Sciences, Poznan, Poland Institute of Meteorology, BOKU, Vienna, Austria KNMI (Royal Netherlands Meteorological [email protected] Institute), De Bilt, Netherlands Global Change Research Centre [email protected] AS CR, v. v. i., Brno, Czech Republic http://stream-ucm.es/Ricardo_Garcia.html - www.knmi.nl/samenw/regioklim/FW - Riederalp-2015 Abstracts Volume 3 LUTERBACHER Jürg Justus Liebig University of Giessen, [email protected] giessen.de http://www.uni-giessen.de/cms/fbz/fb07/ fachgebiete/geographie/bereiche/klima/mitarbeiter/luterbacher MAY Wilhelm Lund University, Sweden [email protected] http://research.dmi.dk/staff/all-staff/wm/ MELO Marián Comenius University in Bratislava, Slovakia [email protected] http://www.fyzikazeme.sk/kafzm/index_en.html PONCRACZ Rita Eotvos Lorand University, Budapest, Hungary [email protected] - SIDERIUS Christian Wageningen University, Netherlands [email protected] http://www.wageningenur.nl/en.htm SOLOMINA Olga [email protected] www.paleoglaciology.org STEPHENSON David [email protected] - STOFFEL Markus [email protected] www.dendrolab.ch STUCKI Peter [email protected] http://www.geography.unibe.ch/content/forschungsgruppen/ klimatologie/forschung/windstorms/index_eng.html TOMASSETTI Barbara [email protected] http://cetemps.aquila.infn.it/chym/Paper TORETI Andrea [email protected] https://ec.europa.eu/jrc/ WHITEHEAD Paul [email protected] http://www.geog.ox.ac.uk/staff/pwhitehead.html Institute of Geography Russian Academy of Sciences, Moscow, Russian Federation University of Exeter, United Kingdom Universities of Geneva and Bern, Switzerland Oeschger Centre for Climate Change Research and Institute of Geography, Switzerland CETEMPS, University of L'Aquila, Italy European Commission, Joint Research Centre, Ispra, Italy University of Oxford, United Kingdom