That challenge brought key scientists, United Nations agencies, national authorities and local practitioners together at UNESCO Headquarters in Paris and online on September 16 and 17, 2026 for a dialogue on High Impact Low Probability Events, Early Warning and Decision Making.
Organized through the joint EU DG ECHO funded CoastWAVE 2.0 and ICG/NEAMTWS initiative under the Intergovernmental Oceanographic Commission (IOC) of UNESCO, the dialogue examined how societies can prepare for rare events with potentially catastrophic consequences. Tsunamis provided the principal case, with discussions extending to volcanic eruptions, earthquakes and disruptions affecting interconnected infrastructure. Denis Chang Seng, IOC Programme Specialist, lead organizer and moderator of the event highlighted that “the dialogue is aimed to build a shared understanding of high-impact, low-probability coastal and tsunami risks and their cascading consequences, strengthen risk-informed governance and multi-hazard early warning under uncertainty, and connect science and planning with community action. It also sought to identify practical follow-up actions.”
Participants emphasized that better forecasting is essential, but protection also requires clear responsibilities, trusted communication and practical arrangements for action. A rare event can overwhelm several systems at once, disrupting power, transport and telecommunications precisely when emergency services need them most.
Olimpia Imperiali, EU DG ECHO said that “the EU Union Civil Protection Mechanism Strategy includes actions to enhance the ERCC’s capacity to prepare for high-impact, low-probability events, while engaging local communities and citizens.”
Scientific discussions explored how uncertainty grows between initial observations, estimates of an earthquake’s rupture and predictions of coastal inundation. Probabilistic modeling and scenarios can help authorities compare protection options. Decisions about acceptable risk, evacuation thresholds and resources remain the responsibility of public authorities.
Stefano Lorito, Coordinator of Tsunami Service Provider of Italy under INGV said: “Science provides estimates with uncertainty; authorities select the desired risk reduction and actions attached to thresholds. The question is whether uncertainty is represented in a form that supports defensible decisions.” Furthermore, Jörn Behrens, Professor of Numerical Methods in Geosciences at the University of Hamburg emphasized that “technical accuracy must be accompanied by clear messages, consequences and instructions for action.” The World Meteorological Organization (WMO) perspective, presented by Muhibuddin Usamah, stressed the connections between hazards and their impacts. “Standard cataloging can connect events and impact data.” Discussions of Krakatau and Hunga Tonga illustrated the need to consider volcanic, atmospheric and tsunami processes together.
For the United Nations Office for Disaster Risk Reduction (UNDRR), a central concern was sustaining attention to risks that fall outside everyday experience. Frequent hazards tend to crowd out rare ones in national roadmaps. Loretta Hieber Girardet, Chief of UNDRR’s Risk Knowledge, Monitoring and Capacity-Development Branch, emphasized that “historical losses alone cannot capture risks beyond recorded experience. Probabilistic modeling and estimates of potential losses can help planning and finance authorities assess the case for investment before disaster strikes.”
UNESCO’s contribution placed communities at the center of the warning chain. “Protection requires people to receive, understand, trust and act,” states a highlighted report passage reflecting the presentation by Carlos Uribe Perez, Programme Specialist at UNESCO for disaster risk reduction.
Experiences from Cannes in France and Kartal and Tuzla in Türkiye showed how maps, signage, education, evacuation procedures and exercises translate knowledge into readiness. For hazards that may not occur for decades, regular drills help create practical experience and preserve institutional memory.
“Rare events do not generate everyday experience, so preparedness must be maintained through repeated communication and exercises,” said Yannick Ferrand, Director of Major Risks for the City of Cannes, France.
Ignacio Aguirre Ayerbe, Disaster Risk Management Senior Lead Researcher at IHCantabria highlighted that “Risk information is not a decision, and a decision is not yet preparedness. Selected hazard zones must be translated into operational evacuation planning, including evacuation routes, assembly areas, travel-time analysis, signage, approved plans and regular exercises.”
The report proposes reviewing national risk assessments and Early Warnings for All roadmaps, strengthening links between scientific experts and decision makers, and testing warning systems under incomplete information, infrastructure failures and simultaneous hazards. Joint case studies and further dialogue were also proposed; these remain recommendations rather than confirmed partner commitments.
The Paris dialogue made the stakes clear: readiness for a rare catastrophe must be built while there is still time to practice, invest and decide.
