David Hondula, Matei Georgescu, & Robert Balling Jr., Arizona State University, Tempe, AZ, USA
Presentation Title: Challenges associated with projecting urbanization-induced heat-related mortality
The aim of this study was to quantify the number of excess deaths attributable to heat in Maricopa County [Arizona, USA] based on three future urbanization and adaptation scenarios and multiple exposure variables. Two scenarios (low and high growth projections) represent the maximum possible uncertainty range associated with urbanization in central Arizona, and a third represents the adaptation of high-albedo cool roof technology.
Subject to urbanization scenario and exposure variable utilized, projections of heat-related mortality ranged from a decrease of 46 deaths per year (-95%) to an increase of 339 deaths per year (+359%). Projections based on minimum temperature showed the greatest increase for all expansion and adaptation scenarios and were substantially higher than those for daily mean temperature. Projections based on maximum temperature were largely associated with declining mortality. Low-growth and adaptation scenarios led to the smallest increase in predicted heat-related mortality based on mean temperature projections. Use of only one exposure variable to project future heat-related deaths may therefore be misrepresentative in terms of direction of change and magnitude of effects.
Key Lessons Learned
- The preference for low growth or urban adaptation strategies depends on key exposure variables.
- Urbanization may contribute to future changes in heat-related mortality.
- Scenario projections are highly sensitive to level of urbanization and exposure variable choice.
- An urban 'oasis' effect emerges in arid and semi-arid climates in which daytime temperatures are often lower in the city center than in the surrounding dry landscape. Urban heating thus primarily concerns minimum/overnight temperatures.