Potential impacts of, and adaptation strategies to extreme sea levels and mean sea level change need to be assessed regionally using consistent methodologies across Europe and between research groups and disciplines. A specific focus is placed on extreme events. Although mean sea level change can be harmful by itself it is the extreme events that have the largest potential for damage, today and also in the future.

Research tasks:

Socio-economic impacts of sea level rise, extremes and adaptation measures on human settlements and human activities need to be assessed and mapped out for our coastal regions.

Adaptation governance and risk management is needed for society in the face of the potential impacts. The efficiency of these measures could be increased if a common methodology was shared.

Changes in extreme sea levels need to be assessed and projected on regional to local scales. This requires the promotion and development of consistent methodologies across Europe and between research groups and disciplines.

Research tasks:

Storm surges and flood risks need to be better known along our coasts, and ideally the same analysis methodologies should be employed across Europe.

Combining extreme sea level estimates with mean sea level projections in order to estimate future extreme levels is an emerging subject of research, and a probabilistic approach to this is recommended.

Changes in storms, wave climate, tidal regimes, and their interaction with changing mean sea levels are subjects not widely incorporated in sea level change research efforts today, but of importance for potential future impacts.

Modelling and projections of regional mean sea level is necessary in order to predict future sea level to help guide mitigation strategies. They need to be improved in order to provide useful local information for assessments of future impacts and adaptation. The development of regional modelling is one of the most important tasks today. A careful analysis of the interaction of the different components affecting the sea level change has to be conducted on semi-enclosed regional seas, as for example the Mediterranean Sea and Baltic Sea.

Research tasks:

The largest and the most uncertain contributions to relative regional sea level change need to be in the focus of research.

Ocean models should resolve the regional physics governing continental shelf and coastal sea level change on a local scale.

Uncertainties need to be reduced and confidence in projections improved.

Upper tail risks of regional sea level rise are particularly important for adaptation of key infrastructure, since they represent low probability, high impact events.

Decadal prediction systems will improve our knowledge of the system and the way we model it.

Reduction of emission scenario uncertainty is a scientific topic of socioeconomics that feeds back to the natural science research on sea level projections.

Observations of sea level and relevant processes are important in order to improve the modelling of future regional sea level change. In some places, vertical land motion may offset sea level rise or may add to it, caused by tectonic processes, large-scale crustal adjustment from previous ice ages, and subsidence. Sea level reconstructions from prehistoric periods from and between previous ice ages can provide constraints on rates and maximum levels of sea level change.

Research tasks:

A combined use of different types of Earth system data is necessary in order to properly understand processes governing variability and long-term change.

Assimilation of high quality observational data into operational models and development of decadal prediction systems is essential for improved understanding of the Earth system, and hence being able to project future changes.

Paleo sea level records help placing modern changes in context and can be used to constrain estimates of future sea level change. Paleo records aid estimations of present and future vertical land motion, which is essential for regional sea level assessments.

ECRA 2nd Joint Collaborative Programme Workshop on

Changes in the Hydrological Cycle and High Impact Events and Climate Change

9 March 2017 | Brussels, Belgium (Helmholtz Association Office)

Goals

The workshop was targeting two goals:

1. Share and discuss recent achievements and challenges in science related to hydrometeorological modelling, extreme events and hydrology

2. Develop a proposal for a dedicated COST Action on the dynamics and impacts of hydrometeorological extreme events under future climate change.

In addition, ideas on related research priorities were collected to be further specified and elaborated to be included in the upcoming “White Paper” of ECRA’s Collaborative Program “Changes in the Hydrological Cycle (CHC)”.

26 scientists (from 19 research institutions in 13 countries) participated in this interdisciplinary workshop, covering the fields of climate science and (eco)hydrology, but also many colleagues with a social sciences background or extensive knowledge in socio-economics, adding particular momentum to the inspiring discussions.

Presentations

The Workshop started with a short introduction about ECRA and the ECRA CPs background as well as an introduction to the fundamentals of the COST Action programme. This was followed by three scientific impulse presentations, successfully stimulating and framing for the following discussions. Jost von Hardenberg (CNR-ISAC, IT) presented model uncertainty aspects in his talk „From high-resolution global climate modelling to precipitation downscaling“, and emphasized the need for intercomparison projects to better understand model differences. Karsten Schulz (BOKU Vienna, AUT) talked about „Challenges in assessing the hydrology of extreme events under climate change conditions“, demonstrating the limits of current practices to trend estimation in extreme event hydrology. Marco Hoogvliet (DELTARES, NE) talked about „Optimization of the climate adaptation process“ and emphasized the user perspective.

Modelling for climate services: Enhancing current knowledge on high impact events and closing key gaps in the underlying science is required to fully realize the European Agenda for climate services. Establishing strong links to potential users of high impact events research are essential. Ensuring the usability of the most up-to-date scientific results will increase the quality and effectiveness of decision-making on e.g. adaptation measures.

Research tasks include:

Characterization of vulnerabilities: Better information produced by improved predictions requires better blending with information regarding exposure and vulnerabilities. This will help to create a resilient response to anticipated risks, taking into account the dynamics of socio-economic activities. Not every extreme event might become a high impact event.

Better quantification of impacts and vulnerabilities associated with extreme climate events can be achieved by linking large and regional scale simulations to physical and economic impact models, recognizing the inherent uncertainties in long-term projections.

Propagation of large scale climate change simulations to the regional scale using statistical downscaling and high resolution regional modelling is a key science topic.

Research tasks include:

The use of statistical methods to improve the value of modelling climate extremes: Statistical techniques such as empirical-statistical downscaling and extreme value statistics offer the possibility to enhance the results of climate models with respect to extreme events and provide a robust probabilistic framing of climate hazards based on e.g. ensembles of climate projections.

Evaluation and improvement of numerical simulations of high impact events, including assessment of the extent to which increases in resolution improve the fidelity of numerical simulations. This is crucial, for developing strategies to improve the reliability of projections for changes in high impact events.

Research tasks include:

Improving regional and local modelling of extreme events: Global high-resolution climate models and regional scale climate models require further developments to e.g. reduce the bias in simulations of the past and thus facilitate more reliable projections of the future. Smaller biases will also facilitate better coupling to impact models.

Climate-related hazards with potential high impacts on human and/or natural systems include extremes such as storms, storm surges, hail, heavy rains and drought. Such events are often of low probability and subsequently existing knowledge drawn from past instances of similar extremes may be scarce or lacking. Therefore, a better understanding of many of the fundamental processes driving the occurrence of high impact events (including the dynamic links with human activities) is critically needed. Only an improved understanding of fundamental processes (including better models) will allow more reliable predictions and projections.

Research tasks include:

Better estimates of historical occurrence frequencies. Two time horizons can be considered here: (i) The near past that is described by observations and reanalysis data (state analysis of the atmosphere and ocean) for the last 50 to 100 years allowing in-depth assessments of selected events (e.g. strong storms), and (ii) The faraway past that is described by carefully collected proxy data which in certain areas can provide a very long record of a particular high impact event (e.g. lake overturning).

Studying mechanisms: (i) Scale interactions in the atmosphere including dynamics/energetics and composition, for example in the context of mid-latitude blockings or tropical cyclones; (ii) Critical processes involved in high impact events, for example the factors that govern the structure and characteristics of extratropical and tropical cyclones, and how these factors are influenced by greenhouse gas and other climate forcings, including stratospheric composition.

How do the statistics of severe weather affect composition and vice versa? Heat waves and future air quality, severe (tropical) storms/convective events (tropical UT/LS composition) and the feedback of changing composition on climate.

Often called the “water towers” of our planet, owing to their role in providing water to the surrounding lowland areas, mountain regions are heavily impacted by climate change. Among the changes in the hydrological cycle components are glacier retreat, decrease of snowpack duration and thickness, changes in precipitation regimes, changes in aquifers, slope stability.

Measuring and modelling the hydrological cycle in mountain areas is challenging. Measurements are difficult owing to the remoteness and harsh environmental conditions of most mountain regions and to the fact that a large fraction of precipitation falls as snow. Modelling of precipitation is also quite demanding, owing to the steep orography and complex atmospheric circulations which put severe constraints on regional and mesoscale numerical models.

This research task will give attention to all aspects of the hydrological cycle in the mountains, from precipitation to runoff, from snow cover changes to glacier and permafrost dynamics, to elevation-dependent warming. It will focus on specific mountain areas of the world such as the Alpine and Apennine regions in Europe and the Himalayas-Tibetan Plateau area, currently subject to intense investigation by several European research groups.

The methods used in this task will involve both data analysis and modelling. The data analysis activities will be conducted in collaboration with national and international programmes such as GEO/GEOSS and in particular its GEO-GNOME Initiative (The Global Network for observation and information in the mountain environments).