Heat waves in the United States: definitions, patterns and trends
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Heat waves in the United States: definitions, patterns and trends Tiffany T. Smith & Benjamin F. Zaitchik & Julia M. Gohlke
Received: 3 September 2012 / Accepted: 25 November 2012 / Published online: 14 December 2012 # Springer Science+Business Media Dordrecht 2012
Abstract High temperatures and heat waves are related but not synonymous concepts. Heat waves, generally understood to be acute periods of extreme warmth, are relevant to a wide range of stakeholders because of the impacts that these events have on human health and activities and on natural environments. Perhaps because of the diversity of communities engaged in heat wave monitoring and research, there is no single, standard definition of a heat wave. Experts differ in which threshold values (absolute versus relative), duration and ancillary variables to incorporate into heat wave definitions. While there is value in this diversity of perspectives, the lack of a unified index can cause confusion when discussing patterns, trends, and impacts. Here, we use data from the North American Land Data Assimilation System to examine patterns and trends in 15 previously published heat wave indices for the period 1979–2011 across the Continental United States. Over this period the Southeast region saw the highest number of heat wave days for the majority of indices considered. Positive trends (increases in number of heat wave days per year) were greatest in the Southeast and Great Plains regions, where more than 12 % of the land area experienced significant increases in the number of heat wave days per year for the majority of heat wave indices. Significant negative trends were relatively rare, but were found in portions of the Southwest, Northwest, and Great Plains.
1 Introduction As mean global temperatures rise (IPCC 2007), there has been increased attention to the frequency of heat extremes and their social and environmental impacts. In 2012 alone, the Intergovernmental Panel on Climate Change (IPCC) issued the full text of their Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change T. T. Smith (*) : B. F. Zaitchik Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, USA e-mail: [email protected] J. M. Gohlke Department of Environmental Health Sciences, University of Alabama at Birmingham, Birmingham, USA
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Climatic Change (2013) 118:811–825
Adaptation (SREX), the Natural Resources Defense Council (NRDC) released the report “Killer Summer Heat: Projected Death Toll from Rising Temperatures in America Due to Climate Change”, and Climate Communications released the report, “Heat Waves and Climate Change.” These studies provide assessments of recent patterns and trends in heat extremes. They also address the complexities involved in evaluating and projecting the frequency and intensity of heat extremes in a changing climate. The occurrence of multiple high profile extreme heat waves in recent years (e.g., Chicago in 1995, Europe in 2003, Russia in 2010) has highlighted the importance of unde
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