Heat Waves

Factors involved: Chemical reactions, geography, human activity, temperature, weather conditions, wind

Regions affected: Cities, coasts, deserts, plains, towns, valleys

Definition

Heat waves occur when the air temperature remains abnormally high for an extended period of time over a region. Heat waves destroy crops; damage infrastructure, such as roads, buildings, and railroad tracks; and cause both animal and human deaths.

Science

Heat waves are the result of a combination of natural factors and human activity. Natural factors include the normal heating of the earth’s atmosphere by short-wave radiation from the sun and long-wave radiation from the earth, the flows of heat that make up the net radiation balance, the tilt of the earth, and the chemical makeup of the atmosphere above the surface of the earth. Human activity, mainly the burning of fossil fuels, is capable of changing the chemical makeup of the atmosphere and thus affects the heating of the earth’s atmosphere.

Normal heating of the earth’s atmosphere occurs when radiant heat, or short-wave radiation, from the sun begins to heat the earth shortly after dawn. Radiation is defined as the transmission of energy in the form of electromagnetic waves. The short-wave radiation is absorbed by the earth. The earth then emits long-wave radiation, which is absorbed by the atmosphere as heat. (Wavelength refers to the distance between the wave crests of successive waves.) In summary, the sun’s rays heat the earth, the earth passes some of this heat to the air, or atmosphere, that surrounds it, and the atmosphere becomes warm. As the air near the earth warms, it rises, and cooler air descends. This rising and lowering sets air currents in motion in the atmosphere. These air currents carry the heat that under certain circumstances can become a heat wave.

A wide variety of factors can affect the amount of short-wave radiation that is absorbed by the earth. About 30 percent of the short-wave radiation coming to Earth is reflected by clouds or dust particles and never reaches the earth’s surface. Another 17 percent of the radiation is absorbed by clouds and other particles in the atmosphere. Thus, a change in the amount of clouds or particles in the atmosphere will affect the amount of radiation that reaches Earth. The condition of the earth’s surface also influences how much radiation is absorbed. The color, composition, and slope of the surface determine how much radiation is absorbed or reflected. Rays that strike the earth perpendicularly are less likely to be reflected. Rays that strike dark soil or dark surfaces are more likely to be absorbed than if they strike light-colored areas.

Carbon dioxide, water vapor, and ozone are the three major components of the atmosphere that absorb the long-wave radiation emitted by the earth, with carbon dioxide absorbing the most. The higher the concentration of these substances becomes in the atmosphere, the more heat is absorbed and the hotter the air becomes. High concentrations of these chemicals also provide a blanket effect over the earth, preventing radiation and heat from escaping. This blanket effect results in a phenomenon called the “greenhouse effect.” In a greenhouse, the sun’s rays pass through the glass and warm the air within the greenhouse. The glass, however, then prevents the heat from escaping. Similarly, the sun’s radiation passes through the atmosphere, warming the earth and the air, and then the atmosphere stops the heat from escaping.

Although the greenhouse effect occurs naturally, it can be influenced by human activity. When fossil fuels are burned, enormous quantities of carbon dioxide are produced and released into the atmosphere. Over the last one hundred years, human beings have increased their use of fossil fuels drastically. Generating electricity, heating buildings, and using automobiles are all human activities that currently depend on burning fossil fuels. Debate continues among scientists as to what role the higher levels of carbon dioxide in the atmosphere and the greenhouse effect play in global warming trends.

When the radiation that leaves the earth is subtracted from the radiation that reaches earth, the amount of radiation left over is called the net radiation. Net radiation affects the earth’s climates and is a source of heat for earth. Thus, all factors that affect radiation to and from the earth will influence the possible development of heat waves.

Geography

Heat waves can occur anywhere on Earth. A wide range of countries have reported heat waves, including the United States, Canada, Russia, India, Japan, many European countries, many African countries, Australia, and Cyprus. Heat waves generally occur over land masses rather than over the oceans. More energy is required to raise temperatures over water than over land, so temperature fluctuations are more prevalent over land. Thus, islands that are surrounded by large bodies of water do not experience heat waves. Since air cools as the altitude increases, mountainous areas are less susceptible to heat waves than are lower areas.

Urban areas tend to have higher rates of heat-related deaths than do rural areas. The heat retention of urban structures contributes to the natural heat of the heat wave. Also, the tall buildings and the pollution of urban areas stagnate the movement of air, thus intensifying the effects of a heat wave.

Many areas of the United States have been affected by heat waves. In 1901, 9,508 heat-related deaths occurred in the midwestern states. During the brutally hot summer of 1936, 15,000 to 20,000 people perished from the heat. In July 1995, heat in the Midwest killed almost 500 Chicago residents. Heat waves have devastated the southern states and have wreaked havoc in both New England and California. Neither Hawaii nor Alaska has recorded a heat wave. Although Hawaii is located near the equator, the Pacific Ocean surrounding Hawaii moderates its temperatures. Alaskan summer days can be hot, but they only go above 90 degrees Fahrenheit occasionally.

Prevention and Preparations

Human beings are powerless to control the natural forces, such as radiation, that affect heat waves. However, human beings can control the amount of fossil fuels they burn, and thus somewhat control the carbon dioxide in the atmosphere. Numerous international conferences have been held to discuss this issue.

Although heat waves are not preventable, both individuals and communities can prepare for heat waves and reduce their harmful effects. Individuals should discuss with family members what they would do during a heat wave and should identify the coolest places to be while at home, at work, or at school. They should learn about places in the community where people can go for help, plan daily activities for the coolest time of day, and refrain from physical activity during the midday hours. Wearing lightweight, light-colored clothing and staying out of the sun can reduce the effects of a heat wave. People should talk to their doctors about any medications or medical conditions that would affect their ability to tolerate heat, as well as learn the signs and symptoms of heat stroke and heat exhaustion and first-aid treatments for these conditions.

Community support programs can greatly reduce loss of life. Those most at risk are the elderly, the poor, and those with health conditions that reduce the ability to tolerate heat. Obtaining air conditioners and fans for those who need them has been effective in saving lives. Establishing “cool centers,” areas that are air-conditioned, where people can go to cool down, can also help reduce fatalities. Media announcements, especially television and radio, inform and alert people to the dangers of heat waves. During the Chicago heat wave of 1995, police officers even went door to door to check on elderly citizens.

Rescue and Relief Efforts

To save lives, rescue and relief efforts must be started as soon as the heat wave hits. The two dangerous medical conditions that result when heat waves occur are heat exhaustion and heat stroke, the latter being the more serious. When someone is exposed to hot weather for an extended time and does not take in adequate water and salt, heat exhaustion occurs. The human body cools itself by sweating; the evaporation of water from the skin reduces body heat. Excessive sweating causes the body to lose large amounts of water and salt. Extended exposure to heat requires the body to sweat profusely in an effort to get rid of heat. If the water and salt lost in this process are not replaced, the body’s attempts to cool itself eventually become ineffective, and heat exhaustion occurs.

The symptoms of heat exhaustion include pale, clammy skin, rapid pulse and breathing, headache, muscle cramps, dizziness, and a sick and faint feeling. If heat exhaustion occurs, the victim should lie down in as cool a place as possible with his or her feet raised slightly, loosen tight clothing, and replace lost fluids by drinking water. One level teaspoon of salt added to each quart (or liter) of water will help to replace the salt lost during excessive sweating. Heat exhaustion must be treated immediately or it will progress to heat stroke.

Heat stroke, also called sunstroke, occurs when the body’s temperature regulation mechanism fails. This mechanism, which is located in the brain, normally helps the body maintain a constant temperature by telling the body to shiver if it needs to become warmer or to sweat if it needs to cool. If a person suffers a heat stroke, this mechanism stops functioning and the body temperature starts to rise to 104 degrees Fahrenheit (40 degrees Celsius) or higher. This is a medical emergency, and medical help should be sought immediately.

The symptoms of heat stroke include flushed, hot, dry skin; strong, rapid pulse; confusion; and ultimately unconsciousness. To treat heat stroke until medical help arrives, victims should be moved to the coolest place possible. Their clothing should be removed, and they should be sponged with cool or tepid water and fanned by hand or with an electric fan. A blow-dryer set on cool may also be used.

Impact

In the United States alone, heat waves have been responsible for the loss of billions of dollars and thousands of human lives. Heat waves damage property, both privately and publicly owned. They kill cattle and destroy crops. Excessive heat causes roads to buckle and crumble, and it warps metal, causing, for example, railroad tracks to bend, resulting in train derailments. Heat waves have been connected to increased cases of riots, violence, and homicides. Sustained heat waves are very difficult for the human body to tolerate. When heat waves occur, normal daily activity must be adjusted in order for humans to survive.

Historical Overview

Throughout history, extremes in temperature have greatly affected human existence. From 543 to 547 c.e., the entire Roman world suffered from plague. Great heat in the area contributed to the spread of the disease. Hot weather caused the flea that transmitted the bubonic plague to speed up its life cycle. The European countries were also affected by wave after wave of disease from 1348 until 1665. Again, the hot summers furthered the spread of the disease.

Detailed weather records from early times do not exist. Information about weather is inferred from the reports of travelers and food availability. Weather reports from the sixteenth century have survived. However, reports based on instrument readings did not appear until the seventeenth century. These records show that periods of high temperature have been recorded for many areas on earth, including Europe, Africa, China, India, Australia, and North America. As time progressed, the records became much more detailed. Thus, much of the information available on heat waves relates to events occurring after the middle of the nineteenth century.

Heat waves have been a contributing factor in human migration patterns. In Ireland, in 1845, hot summer temperatures favored the growth of the organism that caused the potato blight fungus. Failure of the potato crop resulted in widespread famine. Over the next six years around 1 million people died in Ireland. Although an epidemic of typhus contributed to the death toll, hunger played a significant role. Believing that there were more opportunities elsewhere, thousands of Irish people immigrated to the United States.

In the United States, heat waves have been responsible for thousands of deaths and the loss of billions of dollars in the twentieth century alone. The century began with a very hot summer in 1901. It is reported that 9,500 people died that summer. The summer of 1936 was brutally hot; an estimated 15,000 to 20,000 people lost their lives. Those who survived often lost their farms and everything for which they had worked. Again, heat waves influenced migration; families left the “Dust Bowl” area of the middle United States and moved toward the coasts, where more fertile land was to be found.

The air-conditioning of homes began in the 1930s, but it was not in prevalent use. In 1980, only 30 percent of the homes in the United States had air-conditioning, which greatly reduces death tolls during heat waves.

The heat wave of 1980 in the midwestern United States killed 1,265. The heat wave of 1988 resulted in 10,000 casualties. In 1995, almost 500 people in Chicago died within one week. The same heat wave killed 4,000 cattle. The increasing frequency and severity of heat waves worldwide beginning in the last half of the twentieth century generated tremendous concern in the scientific community. Much effort went into studying weather patterns in an attempt to determine whether these heat waves are just part of a natural fluctuation of weather or if human activity is contributing to the warming of the earth.

A heat wave and drought throughout the United States in the summer of 1999 resulted in widespread fires and 502 deaths nationwide, with the state of West Virginia being declared a disaster area. The 2006 North American heat wave, affecting most of the United States and Canada, caused a reported 220 deaths; during this heat wave Los Angeles recorded its highest temperature ever, 119 degrees Fahrenheit.

The states of South Australia and Victoria in Australia suffered a heat wave in 2009, which resulted in bushfires that destroyed more than 2,500 homes and killed 173 people. The heat wave also left more than half a million people without electricity due to the overloaded power grid. During this heat wave, the city of Melbourne recorded a record high temperature of 115.5 degrees Fahrenheit.

In the summer of 2010, a series of heat waves affected the majority of the Northern Hemisphere, including the United States, Canada, Kazakhstan, Russia, Mongolia, China, Hong Kong, South Korea, Japan, Southeast Asia, North Africa, and the whole of Europe. The heat waves were caused by a moderate El Niño event followed by one of the strongest La Niña events ever observed. Russia recorded thousands of deaths as well as wildfires that left thousands more homeless. Japan experienced its hottest summer on record and reported 1,718 heatstroke deaths. In North Africa, particularly Niger, the heat waves exacerbated existing problems with drought and famine.

The Australian summer of 2012–13, known as the "Angry Summer," involved a heat wave affecting 70 percent of the country and broke 123 weather records over a period of ninety days, including a record seven days in a row of average temperatures above 39 degrees Celsius (102 degrees Fahrenheit) across the entire continent. The Bureau of Meteorology had to expand the range of its weather forecasting chart's temperature scale to include temperatures up to 54 degrees Celsius (129 degrees Fahrenheit). Severe bushfires also hit Tasmania, Victoria, and New South Wales, destroying over a hundred buildings.

North America again experienced heat waves in the summers of 2011 and 2012, and in 2013 the southwestern United States and Canada were struck by a heat wave which resulted in temperatures of 129.2 degrees Fahrenheit in Death Valley, California, the highest temperature ever recorded on Earth during the month of June.

From April to June 2015, a severe heat wave occurred in India. By June 2, it had killed a reported 2,330 people, largely in the state of Andhra Pradesh, with some deaths in neighboring Telangana and in the more northern Odisha, making it the fifth deadliest heat wave on record. Roads in Delhi melted, and in Hyderabad, "water camps" opened to provide free water to anyone who needed it.

The damage done by heat waves does not affect all socioeconomic classes to the same degree. The economically disadvantaged suffer more dire consequences when heat waves hit than do those with resources. During the heat wave that struck Chicago in 1995, most of the fatalities were people who were poor and elderly. Most lived in the top floors of old apartment buildings that were not air-conditioned. People with resources obtained air-conditioning or left the city. Farmers are another group of people who are hard hit by heat waves. When heat waves destroy crops or kill cattle, the farmer’s livelihood is destroyed as well. Meanwhile, an accountant who lives in an air-conditioned home in the city pays a bit more for hamburger but hardly notices. In the 2015 Indian heat wave, many of those who died were homeless, and thus had no shelter from the heat. Thus, heat waves affect some social classes more than others.

In other countries, cultural issues can play a role. In July and August, 2003, a severe heat wave in Europe claimed as many as 40,000 victims, many in France. Most homes in Europe do not have air-conditioning, and the effects of the heat wave were worsened by the tradition of August vacations, with few people around to check on elderly residents.

Bibliography

Abrahamson, Dean Edwin. The Challenge of Global Warming. Washington, DC: Island, 1989. Print.

American Red Cross. Heat Wave. Stock Number NOAA/PA 94052. Rev. ed. Washington, DC: US Dept. of Commerce, 1998. Print.

Clayman, Charles B. The American Medical Association Family Medical Guide. 3rd ed. New York: Random House, 1994. Print.

DeBlij, H. J., and Peter O. Muller. Physical Geography of the Global Environment. New York: Wiley, 1993. Print.

Graedel, T. E., and Paul J. Crutzen. Atmosphere, Climate, and Change. New York: Freeman, 1995. Print.

Graedel, T. E., and Paul J. Crutzen. Atmospheric Change: An Earth System Perspective. New York: Freeman, 1993. Print.

Guzman, Andrew. Overheated: The Human Cost of Climate Change. New York: Oxford UP, 2013. Print.

Kirch, W., B. Menne, and R. Bertollini, eds. Extreme Weather Events and Public Health Responses. Berlin: Springer, 2005. Print.

Lyons, Walter A. The Handy Weather Answer Book. Detroit: Visible Ink, 1997. Print.

Oliver, John E. The Encyclopedia of Climatology. New York: Van Nostrand, 1987. Print.

Trenberth, Kevin, Jerry Meehl, Jeff Masters, and Richard Somerville. "Heat Waves and Climate Change." Climate Communication: Science & Outreach. Climate Communication, 28 June 2012. Web. 14 July 2015.

Whiteman, Hilary. "India Heat Wave Kills 2,330 People as Millions Wait for Rain." CNN. CNN, 2 June 2015. Web. 14 July 2015.