Heat waves, global warming, and mitigation.

• Author: Carlson, Ann E.

1. INTRODUCTION II. HEAT WAVE DEFINITIONS A. Heat Waves B. Heat-related Illnesses and Mortality C. Demographics 1. Individual Characteristics D. Place and Space Matter 1. Geographic Differences 2. Intra-urban Differences III. CLIMATE CHANGE AND HEAT WAVES IV. HEAT WAVES AND PUBLIC PERCEPTION A. Disbelief and Blaming the Victims B. Invisibility of Damage and Media C. Heat Waves and Property Damage 1. Media Coverage 2. Government Response to Disasters V. HEAT WAVE MITIGATION A. Heat Wave Emergency Plans 1. When to Issue Heat Wave Warnings 2. Targeting the Warnings and Making them Effective B. The Importance of Air Conditioning 1. Cooling Centers 2. Availability a. Air Conditioning Required b. Funding LIHEAP C. Large Structural Changes 1. Energy Efficiency and Supply 2. Energy Efficiency 3. Reducing the Urban Heat Island Effect VI. CONCLUSION I. INTRODUCTION

   Global climate change is almost certain to increase the frequency and intensity of heat waves. Over the last fifty years we have seen an increase in heat wave events, an increase scientists believe is the result, at least in part, of human activity. (1) The recently released Fourth Assessment of the Intergovernmental Panel on Climate Change (IPCC) concludes that heat waves will "very likely" increase over most land areas over the course of this century. (2) Conservative modeling estimates predict that these increases, absent significant reductions in carbon emissions, will result in a 70% increase in heat-wave deaths in the U.S. over the next forty years. (3)

   Heat waves differ in important respects from natural disasters like hurricanes or earthquakes. Our collective memory about these events fades quickly once temperatures return to normal. Few people seem to remember, for example, that the Chicago heat wave of 1995 killed more than 700 people, (4) or that more than 52,000 Europeans perished in the extreme heat of the summer of 2003--including more than 14,800 in France alone. (5) Even the 2006 deadly heat wave in California, in which at least 140 and as many as 466 people died, has faded quickly from public consciousness. (6) Furthermore, a prolonged U.S. heat wave during the summer of 1980, during which researchers estimate that between 1,500 and 10,000 people perished, has been long forgotten. (7)

   Increased heat waves from climate change are not, of course, the only catastrophic effects expected from global warming. Some of the most dramatic effects may require large structural and political changes. For example, massive sea level rise will require infrastructure investments to protect vulnerable shorelines, and prolonged drought may cause political upheaval and unrest in areas of the world where water is already scarce. The good news about increased heat waves, by contrast, is that we already posses the know-how to respond to the corresponding increase in health risk. Heat waves are not a new phenomenon, and some jurisdictions have made impressive strides in reducing heat-wave deaths. But many jurisdictions across the U.S. are ill-prepared to cope. (8) If Hurricane Katrina and its aftermath have taught us anything, it is that we need local, contextualized preparation (taking into account cultural, social and economic realities) to minimize catastrophe.

   I explore the phenomenon of heat waves in this article for two reasons. (9) First, heat waves already pose a large health threat to our most vulnerable populations and, though we possess the means and know-how to prevent many heat-wave deaths, many U.S. jurisdictions are unprepared to cope. Second, the future looks even worse. As the IPCC Fourth Assessment warns, global climate change will very likely increase the frequency and intensity of extreme heat events over the course of the 21st century. (10) Unless we engage in efforts to mitigate the worst effects of extreme heat, heat death tolls will dwarf current annual rates.

   The numbers of those who die from excess heat annually are already significant: more people die heat-related deaths annually in the U.S., on average, than from any other natural disaster. (11) Though most of us are simply uncomfortable when the temperatures rise, a much more dire consequence of excess heat is a rapid rise in mortality rates, particularly among the most vulnerable populations. The elderly, the poor, the socially isolated, and the mentally and physically ill are at the highest risk of dying of heatstroke and other heat-related illness. Average annual deaths by heat stroke between 1979 and 2003 conservatively total 354 and, in actuality, are likely closer to 1,800 per year. (12) In contrast, annual deaths from hurricanes total 149 (and would plummet to 21 deaths per year if not for the devastating gulf coast hurricanes of 2005). (13)

   Nevertheless, heat waves rarely provoke a massive federal response. The 1995 Chicago heat wave is not even listed on the National Weather Service's top sixty-seven weather-related disasters from 1985-2003 because the compilation of top disasters is based only on whether the disasters caused damages exceeding a billion dollars, not on the number of deaths caused. (14) The 1980 heat wave is listed only because it was accompanied by widespread drought, causing massive agricultural losses. Yet, both the 1980 and 1995 Chicago heat waves rank among the deadliest U.S. natural disasters of the past twenty-five years. (15)

   Current policy and academic attention to climate change is appropriately directed most intensely on efforts to stabilize and ultimately reduce carbon emissions in order to slow the earth's warming. Regardless of those efforts, warming is, and will continue to occur. Accompanying that warming will be more frequent and more intense episodes of extreme heat. (16) Even the most aggressive greenhouse gas reduction efforts will not protect us from some of the negative effects of higher temperatures. Thus, my aim here is to focus not on efforts to reduce carbon emissions but on how to mitigate one of the negative effects of warming--mortality caused by increased heat waves that will inevitably occur.

   I aim, then, to explore strategies to mitigate and/or adapt to increased heat waves in the U.S. Central to any mitigation strategy is the need to understand why the general public and many policymakers pay little attention to the relatively large annual heat-wave death toll. I posit several explanations, drawing from research on risk perception, and ultimately conclude that the lack of property damage from excess heat helps explain why heat waves and heat-wave deaths recede quickly from our collective memory. Indeed, because heat waves cause no property damage, they directly affect a smaller absolute number of victims and generate neither destructive media images nor government sponsored cleanup efforts. As a result, heat waves are less memorable events and, as risk perception studies would predict, recede quickly from our collective memory. I conclude by highlighting heat wave mitigation strategies and linking them to what we know from risk perception literature in order to improve their effectiveness.

2. HEAT WAVE DEFINITIONS

   1. Heat waves.

      Government agencies and the American Red Cross generally define heat waves as extended periods of time, typically forty-eight to seventy-two hours and longer, with excessive heat and humidity. (17) A heat index is used to determine excessive heat, taking into account both temperature and humidity. Research suggests that a particularly important condition contributing to increased morbidity is several consecutive very warm evenings with little wind and little relief from maximum daily temperatures. (18) Excessive heat appears to differ regionally so that a precise definition of a heat wave includes sustained maximum temperatures in excess of average temperatures in a particular area. (19) Even more sophisticated analyses go beyond just measuring temperature and humidity, incorporating types of air masses that surround particular geographic areas to predict the mortality effects of heat waves. (20)

      Several other definitional points are important. Residents of urban areas tend to fare particularly badly in heat waves, in large part because the "built" environment absorbs and retains heat. (21) And residents of northern cities in the U.S. are at a higher risk of mortality from excessive heat than residents of southern cities even though southern cities have on average higher temperatures than northern ones (conversely residents of southern cities fare worse in extremely cold temperatures compared with their northern counterparts). (22)

   2. Heat-related illnesses and mortality

      Estimates of deaths as a result of excess heat come from two separate sources. Some counts include only those deaths where a death certificate lists excessive heat or heat stroke as a cause of death. These are the deaths included in the National Weather Service's estimate of average annual weather fatalities. (23) Heat stroke occurs when the body heats to at least 105 °F and cannot cool itself. Heatstroke happens quite quickly and causes increasingly serious symptoms, including disorientation, delirium and coma. (24) Those who survive heat stroke are at high risk for organ failure and death within a year. (25)

      But heat stroke is not the only cause of increased mortality during a heat wave. Researchers have long noted that average daily death rates increase rapidly during the second or third day of a heat wave and stay elevated during the period of prolonged heat. Individuals with cardiac disease, for example, are at higher risk of death during heat waves because excess heat creates pressure on the cardiovascular system to cool the body; similarly, those suffering from respiratory ailments have an increased risk of death because heat waves are often accompanied by increases in air pollution and small particulate matter. (26) Thus, many death counts for heat waves are calculated by using an "excess mortality" measure, which...