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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.
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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
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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
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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.
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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.
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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
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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
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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.
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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
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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
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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.
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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
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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
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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
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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
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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
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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
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(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.
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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
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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
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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
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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.
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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