The University of Washington School of Public Health
July 29, 2020
By the end of the century, heat exposure may lead to approximately 110,000 premature deaths annually across the United States in a high climate-warming scenario, suggests a new study published in GeoHealth.
Climate change is associated with many adverse effects to human health, including more frequent, more intense and longer heat waves. Exposure to heat can hinder the body’s ability to regulate internal temperature, potentially exacerbating chronic conditions, causing heatstroke or hypothermia, and resulting in death.
“Nobody needs to die in a heat wave — heat wave-related deaths are potentially preventable,” says author Kristie Ebi, a professor of global health and environmental and occupational health sciences at the University of Washington School of Public Health. “I see this study as a call to action to reduce our greenhouse emissions and teach people how to protect themselves in the heat.”
The investigators of this study used information about mean temperatures from the National Oceanographic and Atmospheric Administration (NOAA) and mortality data from the National Center for Health Statistics from 1985-2006 to determine the individual relationship between temperature and mortality for 10 U.S. cities: Atlanta, Boston, Chicago, Dallas, Houston, Los Angeles, Miami, New York, Philadelphia and Washington D.C.
Prior studies of temperature and mortality focused narrowly on specific urban areas. This study went further to analyze the effects of heat exposure across the contiguous United States. To achieve this goal, the investigators used the city-specific data to develop a general mathematical relationship to predict the numbers of U.S. lives potentially lost due to heat exposure at the end of the century. While the mathematical relationship over or underpredicted deaths at the city level, it proved accurate on a larger scale.
Accounting for population growth, the research team applied this mathematical relationship to three possible future climate change scenarios. Each scenario delineates a different potential track for greenhouse gas emissions, from low to moderate to high. “Greenhouse gases are essentially putting energy into the atmosphere; this energy has to go somewhere. These scenarios are used to estimate future temperature change,” says Ebi.
Investigators found that in the current decade, 2010-2020, there were approximately 12,000 heat-related premature deaths annually in the U.S. By 2100, the number of deaths may increase by 36,000 in a moderate-warming scenario and by 97,000 in a high-warming scenario. In a low-warming scenario, where stringent climate policies have significantly limited emissions, deaths remain statistically unchanged from the number of deaths that occur in the current decade.
The study accounts for some forms of human adaption to higher temperatures, such as building improvements or individual changes in behavior, which were found to reduce the impact of heat on mortality by approximately 40-45%. Yet this gain was offset by projected increases in population. Ebi notes the need for more research about how to help people adapt to a warming climate, and awareness is key. “There is a significant research gap on effective ways to communicate that heat is a serious risk. There are effective actions that can be taken by individuals and communities to reduce these risks,” she says.
Lead author of this study was Drew Shindell, the Nicholas Distinguished Professor of Earth Science at Duke University. Co-authors include Yuqiang Zhang, Melissa Scott, Muye Ru and Krista Stark.
Union of Concerned Scientists
Heat Waves and Climate Change
What the Science Tells Us about Extreme Heat Events
Published Jul 31, 2018
Over the coming decades, every region of the US is expected to experience hotter temperatures and more frequent and intense heat waves. This worsening heat poses serious health risks, especially for the very young and elderly, construction and agricultural workers, and those living in the core of urban areas.
These two companion fact sheets summarize:
-The latest science on how extreme heat has changed and is likely to keep changing as global temperatures rise
-The current and potential impacts of extreme heat on people
-How these changes could be curtailed if we take action to reduce the heat-trappingemissions we’re putting into the atmosphere
Extreme heat basics
“Heat wave,” “excessive heat event,” “heat advisory,” “hot spell”—extreme heat has many different names but generally refers to temperatures that are either exceptionally high relative to typical local conditions or reach levels that may be harmful to human health or infrastructure. When extreme daytime temperatures persist over a prolonged period (usually at least two days), it is often referred to as a heat wave.
The human body sweats to cool itself when exposed to high temperatures. In humid conditions, sweat does not evaporate as quickly and the body’s ability to cool itself is compromised. Heat stress can result and, if not addressed, can lead to heat-related illnesses like heat exhaustion and heat stroke. The impacts of temperature extremes on human health and well-being are therefore generally considered in concert with humidity to measure heat stress conditions: those in which the human body has difficulty cooling itself.
Extreme heat now and in the recent past
Extreme heat events can be measured in a few different ways: the maximum temperatures hit (intensity), how often the events occur (frequency), or how long they last (duration). The Dust Bowl era of the 1930s holds the record for peak frequency, intensity, and duration of heat waves across much of the United States to this day—but the frequency and intensity of heat waves have increased in the last several decades in many regions.
In addition to changes in extreme temperatures alone, studies of heat stress trends over the late 20th to early 21st century found increases across much of the country in the conditions that cause heat stress for humans. In a study of changes in extreme heat stress conditions at 187 weather stations across the US between 1949 and 2005, 20 percent of the stations had recorded a substantial increase in the number of one-day, extreme heat stress events (relative to local conditions between 1961 and 1990). On average, these stations recorded 12 more days with extreme heat stress per year in 2005 than they did in 1949.
The future of extreme heat
In the next few decades, if carbon emissions continue to grow, most of the country could see 20 to 30 more days annually with maximum temperatures above 90 degrees Fahrenheit. The Southeast could be hit even harder, potentially enduring 40 to 50 more such days.
By 2100, all parts of the United States are likely to experience more heat waves, with the Southeast, Southwest, and Alaska likely to see the biggest increases. Not only will these heat waves be more frequent, they will also be hotter than what we experience today. If carbon emissions continue to increase substantially, the hottest daily temperatures that occur in a given year in the United States are likely to increase by at least 10°F as compared to the end of the 20th century.
The health effects of extreme heat
Heat is among the deadliest extreme weather hazards in the United States. When exposure to heat is high enough to raise the body’s core temperature, heat stress illness—which encompasses heat cramps, heat exhaustion, and heat stroke—can occur.
With heat cramps, an individual experiences muscle pain or spasms. Heat exhaustion can cause dizziness, a weak pulse, nausea, and fainting. The most severe heat-related illness, heat stroke, occurs when a person’s temperature increases above 103°F. Increased daily air temperatures or periods of extended high temperatures have also been shown to increase cardiovascular mortality, respiratory mortality, and heart attacks.
Some US residents are at greater risk of adverse health effects and death from extreme heat. Low-income residents, the young and elderly, construction and agricultural workers, individuals with pre-existing medical conditions, and people living in the center of urban areas can be more vulnerable to physical harm from heat.
The impacts of extreme heat on daily life
Extreme heat can affect many aspects of daily life and routines, including:
Going to school — The effect of hot conditions on kids diminishes their ability to learn and lowers their performance on tests. Low-income and minority students are disproportionately affected, and research suggests that this is in part because they are more likely to attend schools and live in homes without air conditioning.
Working outside —Millions of people living in the United States work primarily outdoors—construction workers, police officers, farm workers, military personnel, roofers, postal workers, landscapers, and others—and are at risk of heat stress when temperatures soar.
Living in the city —Urban residents face unique heat-related risks in a changing climate. In addition to experiencing the effects of global temperature increases, cities experience temperature increases locally due to the urban heat-island effect. Cities are hotter primarily because they contain an abundance of heat-retaining materials and surfaces, such as asphalt, pavement, and cement.
Living in rural areas —Heat stress also has major implications for rural residents’ livelihoods. For example, heat stress can have negative effects on crop production, as it can adversely affect several processes, including flowering and photosynthesis. Heat stress is also costly to livestock farmers.
Traveling —Many types of infrastructure are affected by extreme heat, including our roads, rails, and air travel. A 2017 heat wave in Phoenix, for example, led to dozens of flight cancellations when temperatures increased to 119° F—above the operable limit of several types of aircraft
What can we do? Preventing the worst consequences
of extreme heat
By stabilizing global carbon emissions in the next few decades (so that atmospheric carbon dioxide remains below 550 parts per million by 2100), the frequency of heat waves the US is likely to see around mid-century would be reduced by approximately 50 percent, compared to a scenario in which carbon emissions continue to increase rapidly through to 2100.
If the global community pursues aggressive emissions reductions in line with the Paris Agreement goal of keeping warming below 3.6°F, the hottest daily temperatures that occur each year in many parts of the country are likely to increase by just 3.6°F instead of by 10°F, as compared to the higher-emissions scenario.
Individuals and communities need policies and infrastructure that take better account of more frequent, intense, and longer-lasting extreme heat. For example, in the coming decades increased reliance on air conditioning to cope with extreme heat is likely to contribute to increased global warming emissions, worsening air quality, and an increase in air pollution–related mortality unless we more aggressively invest in clean energy technology, energy conservation, and energy efficiency measures.
Existing policies also need to be leveraged and new policies enacted to better help people—particularly outdoor workers, children, low-income and minority groups, elderly people, and athletes—to cope with extreme heat. Policies that ensure the safety of all outdoor workers, documented or otherwise, and expand access to and awareness of public cooling facilities are just two examples.
Environment News Service (ENS) Saturday, July 10, 2010
Climate Change Means More Heatwaves, Premature Deaths, Scientists Warn
WASHINGTON – Climate change is a serious health hazard that the United States must prepare for, according to government and university scientists from across the country.
They advised Thursday that climate models show that global warming will increase air pollution and trigger more heat waves, floods and droughts, all of which will threaten human health.
“Climate change is a quintessential public health
problem,” said Michael McGeehin, director of the Division
of Environmental Hazards and Health Effects at the Centers
for Disease Control and Prevention, an agency of the federal government.
“Heat waves are a public health disaster. They kill, and they kill the most vulnerable members of our society,” McGeehin warned. “The fact that climate change is going to increase the number and intensity of heat waves is something we need to prepare for.”
McGeehin was one of several scientists who briefed reporters on a teleconference held by the nonprofit Union of Concerned Scientists.
“Heat waves are a public health disaster. They kill, and they kill the most vulnerable members of society. Climate change is going to increase the number and intensity of heat waves is something we need to prepare for.”
Climate change models show that the kind of heat waves some parts of the country have been suffering through in recent weeks will occur more often and at closer intervals, and last longer, said David Easterling, a climatologist with the National Oceanic and Atmospheric Administration’s National Climatic Data Center.
“The current spate of heat waves could be a harbinger of things to come,” he said, pointing out that from January through May, this year has been the hottest on record for global average temperatures.
Climate change could even make regions of the Earth uninhabitable, according to Matthew Huber, professor of earth and atmospheric sciences at Purdue University. His research on the effects of heat stress, reported in the Proceedings of the National Academy of Sciences, calculated the highest temperature-humidity combination that humans can withstand.
Huber’s findings show that if emissions from burning fossil fuels continue unabated, extremely high temperature and humidity levels could make much of the world essentially uninhabitable for human beings.
Over the long term, the planet could experience an increase of average global temperatures of 10 to 15 degrees Fahrenheit. Under that scenario, much of the world, including Australia, many Mediterranean countries, and parts of Africa, Brazil, China, India and the United States, would be so hot and humid that people would not be able to survive outside during heatwaves for more than a few hours.
“We can still decide to avoid that” by dramatically reducing the heat-trapping emissions that cause global warming, Huber said. “And from our calculations, it is something we should try to avoid.”
Jonathan Patz, director of global environmental health at the University of Wisconsin, Madison, said that while climate change is a health threat, tackling it is a major public health opportunity.
He pointed out that the World Health Organization reports about one million people annually die prematurely from air pollution. He says that cutting global warming emissions also would reduce certain kinds of pollution, especially ground-level ozone.
“If we can reduce air pollution,” Patz said, “we can save lives.”
Patz’s latest research found that cutting down on the number short car trips and reducing the number of miles driven by about 20 percent would save hundreds of lives, avoid hundreds of thousands of hospital admissions, and save billions of dollars in healthcare costs in the Midwest alone.
If drivers got out of their cars and either walked or rode a bicycle, Patz added, “we could probably double those health care cost savings.”
Climate scientist Brenda Ekwurzel with the Union of Concerned Scientists, who moderated the press briefing, noted that addressing climate change is not all about saving polar bears and other faraway creatures and habitats.
“More and more, studies demonstrate that the health care impact and health care costs related to climate change,” she said, “are directly related to us.”
© 2010 Environmental News Service