Early Warning Systems

Early warning systems are means by which people receive relevant and timely information in a systematic way prior to a disaster in order to make informed decisions and take action. The word system is used to refer to the interplay between an array of elements aimed at facilitating communication and prompt response to protect and aid those in need.

There are four basic elements to an early warning system where each part must function efficiently for the system to be successful: 

  • Risk knowledge builds the baseline understanding about risks (hazards  and vulnerabilities) and priorities at a given level.
  • Monitoring is the logical follow-on activity to keep up-to-date on how those risks and vulnerabilities change through time.
  • Response capability insists on each level being able to reduce risk once trends are spotted and announced — this may be through pre-season mitigation activities, evacuation or duck-and-cover reflexes, depending on the lead-time of a warning.
  • Warning communication packages the monitoring information into actionable messages understood by those that need, and are prepared, to hear them.
Community Early Warning Systems (CEWS)

Although often referred to as the “last mile” in an end-to-end EWS, the community is better imagined as the “first mile,” where warning information must at the very least reach and be acted upon. Well-informed communities are familiar with priority risks. Communities are the first responders in protecting their households and disadvantaged individuals. Many communities are motivated and able to independently drive EWS from the local level without waiting for information or warning from the outside while other communities are prepared to receive or monitor warning information and subsequently organize and implement a set of appropriate responses. As seen in the Hyogo Framework for Action (HFA), ‘people centered’ approach goes beyond the concept of the community as a receiver to one where they can also be a producer and facilitator of early warning information. 

Disasters are partly caused by external hazards, but they also stem from vulnerability: people being in the wrong place, at the wrong time, or without adequate protection or resources to respond to a warning. Thus early warnings alone do not keep hazards from turning into disasters. Early action, covering all time scales, is also essential. It is an investment in the future, and has been proven effective at attenuating the effects of disasters. Across the world, significant efforts are being invested in empowering volunteers to take an active role in monitoring risks that influence their communities. As they do so, they learn to both issue, and respond to, warnings that arise from the monitoring. Where and when national early warning systems are active, these community early warning systems complement governmental mandates to protect lives and livelihoods. 


To better understand the definition of a CEWS it is useful to define the terms ‘EWS,’ ‘early,’ ‘warning,’ ‘system,’ ’end-to-end system’ and ‘community’ in that order.

An EWS represents the set of capacities needed to generate and disseminate timely and meaningful warning information that enables at-risk individuals, communities and organizations to prepare and act appropriately and in sufficient time to reduce harm or loss (adapted from UNISDR 2009 and others).

Early signifies prior to the arrival of a hazard or threat — while there is still time to reduce potential harm or loss, or prevent a disaster. A warning is the message (using signs, words, sounds or images) that announces an imminent danger.

system is an ordered and standardized compilation of elements that remain in constant fluctuation with movement in multiple directions. An end-to-end warning system is a complete set of components that connects those who need to hear messages to others who compile and track the hazard information of which messages are composed.

Community represents a network of social interaction that may be exposed to multiple social and/or physical impacts from one or more hazards/ threats, often, but not exclusively, related by place (i.e., village, neighborhood, watershed, etc.).

Based on the terms above, a CEWS is understood to be an effort by or with, but not for, a community to systematically collect, compile and/or analyze information that enables the dissemination of warning messages that when actionable can help the community (or others ‘downstream’) reduce harm or loss from a hazard (or threat) event (or process).

Key Roles

While the primary use for EWS is to save lives and reduce losses to public and private property during a disaster, there are many potential ancillary benefits.  A strong EWS can be used for ongoing communication between the public, disaster managers, government authorities and relief service providers beyond the onset of a disaster, facilitating faster recovery in the aftermath. Underlying all of this there should be strong political and institutional commitment, a body of laws and regulations that support the EWS, and professionals with the appropriate skill set for managing disasters.

Civil society is made up of many entities and groups including the International Red Cross and Red Crescent Movement, international and national NGOs, and community-based organizations. These are institutions whose mandates include supporting governments to protect residents of their country. In EWS, civil society organizations are an important bridge between technical scientific agencies or national governments, and the community, including the all-important volunteer base on which the community depends. They have the distinct advantage of knowing particular communities well and also of having the capacity to interpret early warning information compiled outside the community.

Governmental institutions must be held accountable for ensuring that EWS reach the entire at-risk population, and are acted upon in a timely fashion. Entities most often engaged in early warning are the national disaster risk reduction/ management agencies/units as well as the meteorological, hydrological and health services. National EWS and/or these services most often have representatives at sub-national level, especially in areas exposed to the greatest risk.

Disaster – A serious disruption of the functioning of a community or a society involving widespread human, material, economic or environmental losses and impacts that exceed the ability of the affected community or society to cope using its own resources.

Disaster risk reduction – The concept and practice of reducing disaster risks through systematic efforts to analyse and manage the causal factors of disasters, including through reduced exposure to hazards, reduced vulnerability of people and property, wise management of land and the environment, and improved preparedness for adverse events.

Early warning system – The set of capacities needed to generate and disseminate timely and meaningful warning information to enable individuals, communities and organizations threatened by a hazard to prepare and to act appropriately and in sufficient time to reduce the possibility of harm or loss.

Hazard – A dangerous phenomenon, substance, human activity or condition that may cause loss of life, injury or other health impacts, property damage, loss of livelihoods and services, social and economic disruption, or environmental damage.

Mitigation – The lessening or limitation of the adverse impacts of hazards and related disasters.

Preparedness – The knowledge and capacities developed by governments, professional response and recovery organizations, communities and individuals to effectively anticipate, respond to, and recover from the impacts of likely, imminent or current hazard events or conditions.

Prevention – The outright avoidance of adverse impacts of hazards and related disasters.

Public awareness – The extent of common knowledge about disaster risks, the factors that lead to disasters and the actions that can be taken, individually and collectively, to reduce exposure and vulnerability to hazards.

Resilience – The ability of a system, community or society exposed to hazards to resist, absorb, adapt to and recover from the effects of a hazard in a timely and efficient manner, including through the preservation and restoration of its essential basic structures and functions.

Risk – The probability of an event and its negative consequences.

Vulnerability – The characteristics and circumstances of a community, system or asset that make it susceptible to the damaging effects of a hazard.