Early Warning Systems Defined - Reducing Disaster: Early Warning Systems for Climate Change - page 87

or hours of lead time for a warn-on-forecast system. Hurricane warnings are on the
order of hours to weeks. Drought warnings are sometimes issued months in advance.
Yet an EWS does not start with a hazard manifesting. As Mileti et al. ( 1999 ,
pp. 174-175) wrote:
The most effective warning systems integrate the subsystems of detection of extreme events,
management of hazard information, and public response and also maintain relationships
between them through preparedness.
EWS as a social process means that it should be ongoing, engrained in the
day-to-day and decade-to-decade functioning of society—even while recognising
that this ideal is rarely met in practice. To understand the operationalisation of this
ideal for an EWS, the phrase itself needs to be broken down.
Box 5.2 EWS Questions
• How early is 'early', especially in relation to the timing of the warning
compared to the timing of the hazard—and of the vulnerability?
• What constitutes a 'warning'—just the information about the hazard or
more?
• How is that warning triggered?
• What is meant by a 'system': formal, informal, quantitative, qualitative, or
anecdotal?
• With EWS engrained in a community, what else might it contribute to,
other than the strict EWS functions?
The answers to the questions in the box are contextual, varying amongst social
settings and also depending on the hazard or hazards to which an EWS is geared.
For example, the USA runs two offi cial tsunami warning centres:
(i) The West Coast and Alaska Tsunami Warning Center based in Alaska which is
responsible for issuing tsunami warnings for most American and Canadian
coasts, but not including Hawai'i, the US Pacifi c territories, and Canada's
Arctic.
(ii) The Pacifi c Tsunami Warning Center in Hawai'i which is responsible for issu-
ing tsunami warnings for much of the rest of the world, including the Pacifi c
and Indian Oceans.
These centres' responsibilities include sending out messages regarding tsunamis
as soon as possible, usually within minutes, after a potentially tsunami-generating
earthquake. As such, 'early' means immediately after a hazard manifests while
'warning' means a message with quantitative hazard parameters that identifi es
coastlines which might experience a tsunami.