European Windstorm Insurance Industry “Key Questions” Short Descriptions

CATIN SIGHT 02 EUROPEAN WINDSTORM - INSURANCE INDUSTRY “KEY QUESTIONS” - SHORT DESCRIPTIONS 03

01. Natural variability of Europe Windstorms vs. cycles vs. trends/

There has been a geographical shift of windstorm activity in recent years whereby France has been hit by four windstorms and the UK has remained relatively quiet. Furthermore, models are starting to include a “short term” view of risk to allow for the fact that windstorm activity is perceived to have decreased in the past 20-25 years.

• Are these changes natural variability of part of an ongoing climate-related trend? • Can we develop a better understanding of the natural variability “mechanisms” (e.g. NAO) and their relation to storminess?

02. in the tail: better understanding limits to EUWS footprints: intensity, size, shape

There is concern within the catastrophe modelling industry y that the storms that inhabit the tail of the curve (i.e. event with loss return periods of >200 years) have a size and direction unlike the most severe historical storms.

• Can we get some more data-points from the “tail” of climate model runs to sit alongside existing catastrophe model output as a “second set of eyes”?

03. Correlation between wind and flood risk

There is currently very little understanding (or indeed implementation in catastrophe models) of the correlation between wind and flood in Europe.

• Do that possess multiple damaging windstorms also contain loss-making flood events? • How well correlated are wind and flood hazards not just in the tail but at shorter return periods? • Do stormier mean that the chance of an event with both wind/flood losses is greater owing to antecedent conditions? 04 EUROPEAN WINDSTORM - INSURANCE INDUSTRY “KEY QUESTIONS” - SHORT DESCRIPTIONS

04. Academic data to expand our understanding of historical EUWS

Similar to the “Winter storms in Europe: messages from forgotten catastrophe” study:

• Can we look at recent storms of the past 150-200 years, produce footprint and potentially the uncertainty around them from running re-analyses. • Are there are other sources of historical data/reanalysis that exist which could be used to understand historical precedents?

05. Spatial correlation of hazard (and loss) across different countries

Differences in cross-country correlation are a big driver of portfolio-level loss differences for reinsurers who have European-wide books of business. It would be useful to understand better the hazard correlation between countries (e.g. peak gusts, Severity Index). Potential also (e.g. through OASIS) to translate any hazard correlation research into loss correlation using vulnerability curves.

• Can we translate climate research output into understanding of the multiple aspects of hazard that influence the amount of correlation between different countries?

06. Clustering: better understanding on frequency/severity

Although research has been done to look into clustering, it does vary greatly between catastrophe models.

• Can we use climate models and synthetic event sets produced from these models to improve our understanding of event clustering? • Can we here also to understand better the relationship between clustering and event severity? EUROPEAN WINDSTORM - INSURANCE INDUSTRY “KEY QUESTIONS” - SHORT DESCRIPTIONS 05

07. Creation of open source EUWS cat models through academia

Other views of windstorm risk are always welcome in the insurance industry as an extra pair of eyes to compare against existing vendor windstorm models.

• One suggestion is whether there is potential to piggy-back off existing climate model data to provide an alternative view – per item 9) here? (One initiative is under way with the Copernicus WISC project providing 4km storm footprints).

08. Understanding the impact of choice of climate model resolution on the resultant view of risk

Part of the concern in item 2) above comes from the hypothesis that storm shape/size is related to the base model resolution when using a climate model.

• What is the coarsest resolution of GCM that can still be useful and provide adequate data for dynamical downscaling? • What resolution of GCM can be useful for risk assessment without having to do dynamical downscaling (i.e. perform statistical downscaling on the dataset)? • Also, can we get some understanding around calibration techniques for climate models to understand the biases and how/when to correct them? • What are the best statistical downscaling techniques and what is useful from GCM and what is not reliable?

09. Improving understanding of EUWS through repurposing pre-existing high-res GCM data

This is essentially a catch-all for a number of these topics, but it has been kept in nonetheless.

• How much GCM data is out there that has enough “years” of data at an appropriately high enough resolution to make it useful to repurpose it for risk estimation studies? 06 EUROPEAN WINDSTORM - INSURANCE INDUSTRY “KEY QUESTIONS” - SHORT DESCRIPTIONS

10. High-frequency low severity wind events (winter and )

This one is potentially one to stay within the industry to solve. We rarely get detailed loss information to understand the impact of low severity wind events (e.g. convective summertime wind events as well as small wintertime events).

• Is there any data out there to help us understand better the impact of these low severity (both winter and summertime events?) • Is there a way of standardising a definition of what makes a high frequency, low severity event?

11. Crossover of hurricane & EUWS . Influence of hurricane remnants on EUWS, now & future

Hurricane remnants that re-intensify over Europe as extratropical storms (the example of Hurricane Lili was used when list created, obviously we have Ophelia now) are something we arguably know little about in terms of potential.

• Could there be tail events that include this type of event? • Is there a role of warm air associated with hurricane affecting early-season windstorms to give them increased potential? • Does the suggested future atmospheric/oceanic warming in future extend the crossover region between hurricanes and re-intensifying systems further NE into the Atlantic?

12. Forecasting of storm/flood events at the localised level

Primarily improvements in forecasting here would help the industry with business preparedness and claims handling.

• Rapid development of European storms makes it difficult to increase the time element of warnings beforehand: can this be improved? • Can we improved very local forecasting: which in particular would help for flood forecasting. 07

Credits

CATIN SIGHT

Dr Claire Souch Dr Richard Dixon Director, AWHA Consulting Limited Director, CatInsight lighthillrisknetwork.org

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