Disaster early warning systems: What works and who gets left behind? 

Extreme weather and climate-related events are increasing in frequency and intensity, causing substantial loss of life, injuries, displacement, livelihood disruption and economic damage. Early warning systems have been widely used for mitigating the impact of extreme weather events, and several individual studies have assessed their effectiveness in improving outcomes. However, there is very limited comprehensive synthesis of evidence from these studies to establish whether existing early warning systems work, for who, at what cost, and the conditions that facilitate their successful implementation.  

We conducted a comprehensive systematic review of the available literature to assess the effectiveness of existing early warning systems, their cost-effectiveness, the barriers and enablers to their successful implementation, and the views of target populations and communities regarding their usefulness. The research was guided by a consultation group of experts in systematic review methods as well as practitioners and researchers in disaster risk management, to ensure that the findings are relevant to policy and practice.  

The systematic review included synthesis of 111 studies published between 1995 and 2026, covering 54 countries and a wide range of hazards – including floods, cyclones, hurricanes or typhoons, droughts, extreme heat, earthquakes, tsunamis, landslides and wildfires. Most of the early warning systems were operated at the national level, but community-based or locally operated systems were particularly common in lower-income settings and were often focused on mitigating the impact of flooding or heavy rains.