The year 2016 broke temperature records around the world. For a brief period during the summer, 124 million Americans across the United States were under extreme heat advisories, watches, or warnings issued by the National Weather Service. Across the globe in Mitrabah, Kuwait, a weather sensor documented what is possibly the highest temperature ever recorded in Asia: a staggering 129.2° F (54° C). With global temperatures steadily ticking upwards and new records being set year after year, public health officials in particular are paying close attention to the impacts of rising temperatures on the incidence of lethal heat events.
Data from the National Centers for Environmental Information show record-breaking average temperatures across the United States throughout summer of 2016 (NOAA/NCEI).
In the United States, extreme heat causes more deaths than any other weather-related hazard. Over seven thousand Americans succumbed to the impacts of extreme heat exposure between 1999 and 2009. Physical factors are an important determinant of vulnerability, and small children, elderly people, and individuals with respiratory or heart conditions are at elevated risk during periods of high heat. Psychological factors play an important role in determining vulnerability, too. For example, if an individual doesn’t know the causes or symptoms of heat stroke, or if they are unaware of structural risks in their community’s water, food, or energy supply systems, they are potentially much more vulnerable to the impacts of a heat wave. In other words, knowledge about one’s own vulnerabilities is part of being adequately prepared.
In response to an extreme heat event, Americans are advised to take precautions like drink more water, avoid direct sunlight or strenuous activity, and ensure that pets and young children remain cool and hydrated. People who take heat risk seriously or have been personally affected by an extreme heat event in the past may be more likely to take such precautionary measures or heed government advisories when an extreme heat event is ongoing or imminent.
In 2013, a survey conducted by the Yale Program on Climate Change Communication found that 85% of Americans had experienced one or more types of extreme weather in the past year, with over half specifically citing extreme heat. Americans accustomed to warm summers with lengthy stretches of high temperatures are likely more familiar with the risks associated with extreme heat events. Preliminary results from national surveys conducted in 2015 by Dr. Peter Howe of Utah State University and the YPCCC show that heat wave risk perceptions in the United States are higher-than-average in southern states and lower-than-average in northern states. Southerners may perceive heat waves as a greater risk than northerners because they have more personal experience with extreme heat events.
Heat wave risk perceptions depart from the national average in a north-to-south pattern. Climate-induced changes in the distribution of heat waves may impact individuals with low perceptions of heat risk (Howe, Marlon, and Leiserowitz, unpublished data).
Rising temperatures due to increasing greenhouse gases, however, are creating a mismatch between the distribution of extreme heat events across the United States and the risk perceptions of individuals impacted by those events. In some places where extreme heat days will become much more frequent—states like Wyoming, Utah, Montana, and Colorado in the West, as well as Midwestern states like Minnesota, Nebraska, and North Dakota —perceptions of heat risk are lower than the national average. Model projections show that the incidence, duration, and severity of extreme heat events will continue to increase across the United States as the climate warms. The result is a potential public health crisis that will be aggravated by climate change, as extreme heat events begin affecting people with low perceptions of heat risk and little prior experience of extreme heat. When risk perception does not match threat, individuals and communities may become especially vulnerable to natural hazards.
Models project a significant increase in the number of heat days experienced in the United States between the late 20th century and late 21st century (Lau & Nath, 2012).
How should public health officials respond to a likely increase in future heat waves? Communicating the risks of extreme heat should play a central role in policymakers’ response. To assess perceptions of heat risk around the United States, the YPCCC and its partners have undertaken a new project funded by the National Science Foundation that will survey Americans’ beliefs and attitudes about extreme heat risk. YPCCC’s heat risk research will fill a critical knowledge gap by systematically describing heat risk perceptions at national and sub-national scales, with data covering rural and urban areas. Particular attention will be paid to the role of personal experience and socioeconomic factors in determining individual perceptions of heat risk. The net result will be a comprehensive picture of heat risk perception across the United States at the state and community level, information that will be valuable to public health officials aiming to tailor their communication strategies regarding heat risk to the unique attitudes and beliefs held by members of their communities. These communication strategies will be especially important in regions where perceptions of heat risk may not match the incidence or severity of extreme heat, like the Midwest and Rocky Mountain regions.
This research is funded by NSF grant #DRMS-1459872 to PIs Jennifer Marlon, Peter Howe, and Anthony Leiserowitz. More information on YPCCC’s heat risk research is available here: http://climatecommunication.yale.edu/about/projects/heat-wave-risk-perceptions/.
 “Oppressive summer heat grips large portions of U.S.” National Oceanic and Atmospheric Administration, 22 July 2016:
 “Temperature in Kuwait hits 54 Celsius, sets possible record amid Middle East heatwave – UN.” United Nations News Service, 26 July 2016: http://www.un.org/apps/news/story.asp?NewsID=54559#.WJ3Q1hIrKRs
 “The Health Impacts of Climate Change on Americans,” The White House. https://obamawhitehouse.archives.gov/sites/default/files/docs/the_health_impacts_of_climate_change_on_americans_final.pdf
 Leiserowitz, A., Maibach, E. W., Roser-Renouf, C., Feinberg, G., & Howe, P. (2013). Extreme Weather and Climate Change in the American Mind, April 2013.
 “Modeling geographic variation in risk perceptions as a component of social vulnerability to extreme heat hazards in the U.S.” Presentation by Howe, P.D., Marlon, J.R., Leiserowitz, A., American Association of Geographers Annual Meeting: 23 March 2016.
 Lau, N.-C. & Nath, M. J. (2012). A Model Study of Heat Waves over North America: Meteorological Aspects and Projections for the Twenty-First Century. Journal of Climate, 25, 4761–4784.