GC089-06
Global Urban Population Exposure to Extreme Heat
Monday, 14 December 2020: 05:50
Virtual
Cascade Tuholske, University of California Santa Barbara, Department of Geography, Santa Barbara, CA, United States, Kelly K Caylor, University of California, Santa Barbara, CA, United States, Christopher Funk, USGS, Baltimore, MD, United States, Andrew Verdin, University of Minnesota Twin Cities, Institute for Social Research and Data Innovation; Minnesota Population Center, Minneapolis, MN, United States, Stuart Sweeney, Pasadena, CA, United States; University of California Santa Barbara, Geography, Santa Barbara, CA, United States, Pete Peterson, University of California Santa Barbara, Santa Barbara, United States, Tom Evans, University of Arizona, School of Geography & Development, Tucson, United States and Kathryn Grace, University of Minnesota Twin Cities, Minneapolis, United States
Abstract:
Rapid population growth and increased extreme heat due to climate change pose significant challenges for the planet’s urban areas. Yet, how global urban exposure to extreme heat is changing has yet to be quantified and mapped at a fine spatiotemporal resolution. Here we estimate daily urban population exposure to extreme heat for 13,115 cities from 1983 to 2016. To accomplish this, we harmonize a new quasi-global, fine-resolution (0.05°) daily temperature maxim estimates with the first globally uniform, geo-located urban population and spatial extent dataset (see supplement). For each urban area, we calculated area-averaged daily heat index maximums following the US National Oceanic Atmospheric and Administration’s procedure using Climate Hazards center InfraRed Temperature with Stations daily temperature maximum (CHIRTS
daily) data and down-scaled daily humidity estimates from ERA5 climate reanalysis. We then measure the average annual rate of increase in exposure (person-days yr
-1) at the global, regional, national, and municipality-level from 1983 - 2016. At each spatial scale, we measure and map the relative contribution to the increase in exposure from population growth versus urban warming.
Globally, exposure increased almost 150%, from 118 billion total person-days in 1983 to 291 billion person-days in 2016. Exposure grew at a rate of 5.2 billion person-days yr-1, of which population growth contributed 3.9 billion person-days yr-1. Urban warming comprised 26% of the annual rate of increase in exposure, contributing 1.4 billion person-days yr-1. At the municipality-level, the annual rate of increase in exposure from 1983 - 2016 was statistically significant (p < 0.05) for 62.7% of urban areas globally. However, the contributions of population growth and urban warming to increased exposure exhibit high spatial heterogeneity. These results highlight an urgent need to implement locally appropriate early warming, adaptation, and mitigation strategies to temper the harmful and inequitable impacts of urban extreme heat exposure.
