Spatial Approach of Climate Risk Assessment and Uncertainty: A Case Study of Heat Wave Risk in Seoul

As climate change continuously reaches new climaxes, it is aggravating many climate extremes. Urban heat island effect (UHI) is one of them. It occurs in cities with sealed surfaces and building canyons, which make changes in storage, radiative and turbulent heat flux that make cities warmer than surrounding areas. However, applying adequate policies at the right place can attenuate the impacts of UHI. Therefore, heat wave risk assessment is important in the sense that it helps decision makers set priority in targets of application. Seoul is highly urbanized capital of South Korea. It is suffering from increasing heat wave days and tropical nights every year. More than 10 million residents are exposed to heat extremes and measures should be taken. Therefore, heat wave risk assessment of Seoul should be done in advance. While, risk assessment contains uncertainty; from variables to assessment procedure. However, there is no standardized assessment methodology. A fuzzy logic, introduced by Zadeh in 1965, is applied in quantifying these uncertainties. We fuzzified indices for assessing heat wave risk with threshold values. And indices were aggregated step by step with fuzzy operators, which make up "vulnerability" and "climate exposure". Vulnerability and climate exposure are further combined with fuzzy operator to derive complete heat wave risk assessment map. As a result, we expressed spatial distribution of UHI risk. Districts lying in the central area of the city showed higher risk than in marginal areas. In addition, hierarchic structured approach of assessing risk in this study makes it easy to track key variables of risk, therefore, giving decision makers insights to help their application of adaptation policies.