Exploring the Changing Nature of Heat Hazards in a Geographically Diverse State

Recognized by the National Weather Service as the leading weather-related cause of mortality in the United States (and around the world), heat waves are a ubiquitous hazard. The nature of heat hazards is complex, consisting of both objective components related to thermoregulation and relative components with roots in the acclimatization of the individual or community at risk – dependent on the geography of the region and the community in question. Boasting the largest elevation span (6,684 feet) of any state east of the Mississippi River, North Carolina contains a wide variety of geography from the Appalachian Mountains to the Outer Banks, and is organized by the National Oceanic and Atmospheric Administration (NOAA) into 8 climate divisions. Understanding how projected changes in heat extremes may differ across climate divisions is critical in helping communities of all types prepare for and adapt to an uncertain future.

To this end, we assess the potential evolution of heat extremes in North Carolina and how that evolution may differ across its diverse geography. With a wide disparity in climatological heat values across the state, we evaluate extreme heat using intensity-duration-frequency (IDF) curves, controlling for the relative geographic factors associated with heat hazards. Traditionally used for hydrological applications, IDF curves estimate the expected return period (or frequency) of an extreme event given its intensity and duration. Using downscaled CMIP5 and CMIP6 projections, we aggregate heat extremes up to the climate division level and evaluate short- and long-term events to track heat hazards across the temporal spectrum. Furthermore, recognizing that factors beyond dry bulb temperature have a significant impact on event severity, human health metrics (such as heat index) are also incorporated into the IDF framework. And while a greater understanding of future extreme heat event characteristics is crucial, assisting with community adaptation and mitigation measures is equally important - thus, we highlight initiatives in North Carolina aimed at making our communities and citizens more resilient to increasing heat stress.