A systematic approach to identify 'unknown unknowns' for impact-based early warning systems

Climate change brings emerging complex risks, subtle and weak, starting to manifest in some regions around the world, followed by the recurrence of preventable tragedies across regions. For instance, in Macau in 2017, people drowned in flooded underground car parks as they tried to save their vehicles. Tragically, similar preventable tragedies have since recurred in South Korea (2022) and Spain (2024). Before these incidents, local disaster risk reduction strategies in Macau, South Korea, and Spain did not cover specific guidelines addressing the resilience of underground spaces to extreme weather. Although local governments eventually enhance their regulations, such action is typically a reactive measure, triggered only by catastrophe rather than proactive foresight.

The primary obstacle to foresight is the challenge of identifying ‘unknown unknowns’—rare, variable-severity emerging risks. Our study directly addresses this critical gap in the early warning chain by demonstrating a systematic methodology that leverages cross-regional knowledge of analogous events to identify ‘unknown unknowns’ for regions without prior experience, thereby transforming them into foreseeable risks and enabling proactive preparation and strengthening response capabilities.

This study utilizes Natural Language Processing to analyze 7.7 million news articles across four dimensions—public awareness, priority of human needs, level of severity, and scope of influence—identifying 639 emerging climate threats, subsequently refined by an expert intervention to pinpoint the most critical tail-end risks. The findings uncover a wide spectrum of lesser-known emerging risks across diverse sectors, such as health, food, infrastructure, finance, transportation, and wildlife-related threats. An example of the findings is a paradox, first identified in peer-reviewed research and subsequently reported by the media. This paradox reveals that mercury in fish is increasing even as oceanic mercury declines, a phenomenon driven by warmer seawater that compels fish to migrate to cooler regions, which in turn elevates their energy consumption and accelerates bioaccumulation.

Ultimately, this research provides a practical decision-support tool for a range of stakeholders. By translating ‘unknown unknowns’ into actionable insights, our methodology enables a paradigm shift from reactive post-disaster response to proactive risk management. Specifically, these identified risks can be used to inform targeted risk communication strategies and establish triggers for anticipatory action. This provides a crucial component for the UN’s ‘Early Warnings for All’ (EW4All) initiative, enabling communities and disaster managers to prepare for emerging complex risks before they manifest as localized crises.