Geoscience Reference
In-Depth Information
Box 2.1 Defi nitions
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” (UNISDR 2009a )
Natural hazard:
“Natural process or phenomenon that may cause loss of life, injury or other health impacts,
property damage, loss of livelihoods and services, social and economic disruption or envi-
ronmental damage” (UNISDR 2009a )
Climate Extreme (extreme weather or climate event):
“The occurrence of a value of a weather or climate variable above (or below) a threshold value
near the upper (or lower) ends of the range of observed values of the variable” (IPCC 2012b )
Disaster:
“A serious disruption of the functioning of a community or a society involving widespread
human, material, economic or environmental losses and impacts, which exceeds the ability
of the affected community or society to cope using its own resources” (UNISDR 2009a )
2.1.1
Hazards Versus Disasters
The United Nations International Strategy for Disaster Reduction (UNISDR)
released a compilation of updated standard terminology related to disaster risk
reduction in order to mainstream terms and their defi nitions (UNISDR 2009a ). See
Box 2.1 for a defi nition of hazard, natural hazard, and disaster.
There exist a variety of definitions for extreme events; the definition in Box
2.1 is from the IPCC SREX report (IPCC 2012a ). The word extreme can be used to
describe the impact of the event or physical aspects of the event itself, which can
lead to confusion. In general, extreme events, for example related with temperature
or precipitation, can be defi ned by indices describing absolute quantities or the fre-
quency of incidents beyond an absolute or relative threshold or by dimensionless
indices (Zwiers et al. 2013 ). Natural hazards and extreme events fall into the same
context and can be used interchangeably.
Disasters and natural hazards/extreme events are often associated with each
other but they are not the same. A disaster is the result of the severity of a natural
hazard combined with the exposure to the hazard, the preexisting vulnerability, and
the inability to cope with the impacts of the hazard (UNISDR 2009a ). Examples of
common hazards are hurricanes (Figs. 2.1 and 2.2 ), droughts, fl oods (Fig. 2.3 ), and
forest fi res (Fig. 2.4 ).
Not every extreme event has to lead to a disaster; it largely depends on the pre-
vailing conditions (IPCC 2012a ). The prevailing conditions are determined by the
level of vulnerability and exposure of populations. Exposure and vulnerability are
 
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