Hurricanes: Their Nature and Impacts on Society - Climate Science ...

64 HURRICANES: THEIR NATURE AND IMPACT ON SOCIETY
Obviously, such trend data are not a reliable indicator of the causes of
impacts. What is needed is a conceptual framework within which tropical
cyclone impacts <strong>and</strong> the various methodologies used to interpret them can be
broadly understood. The concept of vulnerability provides such a framework.
2.3.2 Societal vulnerability to tropical cyclones: a framework for assessment
Clearly, there are a wide range of factors important to underst<strong>and</strong>ing tropical
cyclone impacts. Further, different decision-makers will need to underst<strong>and</strong>
impacts in different ways, depending upon the particular policy decisions that
they face. This section uses the concept of "vulnerability", as described in
Section 2.2, as an integrative framework within which one can more reliably
assess preparedness for tropical cyclone impacts in broad context.
The impacts of tropical cyclones on society are a result of both physical <strong>and</strong>
societal factors. If the term event incidence is used to refer to the physical
aspects of tropical cyclones <strong>and</strong> societal exposure is used to refer to social
conditions, then vulnerability to tropical cyclones can be defined as a function
of incidence <strong>and</strong> exposure. Thus, vulnerability of society to hurricanes can be
defined as follows:
vulnerability = f(incidence, exposure)
Society mitigates its exposure, <strong>and</strong> consequently impacts, through conscious
action which we call "preparedness". Preparedness reduces exposure, <strong>and</strong>
consequently vulnerability. The concept of vulnerability provides a framework
for an assessment of tropical cyclones <strong>and</strong> can suggest causes of impacts,
consequences, <strong>and</strong> alternative actions for improving preparedness.
Vulnerability assessment requires knowledge of incidence, exposure, <strong>and</strong>
preparedness. Incidence is determined through climatology <strong>and</strong> meteorology.
Factors that are important in assessing incidence include frequency, magnitude,
location, intensity, etc. Exposure is determined through assessment of
people <strong>and</strong> property at risk to the event. Assessment of both tropical cyclone
incidence <strong>and</strong> exposure to tropical cyclone impacts can be both backwardlooking
(e.g. the climate record, demographic trends) <strong>and</strong> forward-looking
(i.e. forecasts, projections). Preparedness assessment is more difficult to perform
<strong>and</strong> is consequently least often undertaken. It involves asking questions
such as "How prepared are we?" <strong>and</strong> "What steps can be taken now to reduce
the impacts of future events?" The answers to these questions are of course
intimately related to knowledge of incidence <strong>and</strong> exposure.
Vulnerability is a useful concept because it helps the analyst to recognize
explicitly that there are both physical <strong>and</strong> social causes of impacts. It is more
difficult to discern the balance of physical <strong>and</strong> social factors driving impacts
from simple trend data on losses or casualties. For instance, some, like the US