Temperature spikes spanning several days or more will rack up a higher body count in the eastern United States during the coming century than they have in the past, according to a new study.
Heat waves are the deadliest weather phenomenon in the United States, killing more people annually than hurricanes, floods, earthquakes and tornadoes combined, according to the Centers for Disease Control and Prevention. High temperatures can directly cause harm through heat stroke and dehydration, but can also send people to emergency rooms by making heart and lung problems worse.
With average temperatures rising, researchers project that periods of surging heat will become more frequent and more intense.
In a study published earlier this month in the journal Environmental Health Perspectives, scientists projected how many excess deaths from heat would occur in the eastern portion of the United States.
Yang Liu, one of the report's authors and an assistant professor at the Rollins School of Public Health at Emory University, explained that he and his collaborators used high-resolution climate models, looking at the country in 4-kilometer-square chunks. The resolution also made the simulation more computationally intensive, so the scientists limited their assessment to only part of the country.
Nonetheless, the region spanning from Maine to Florida is home to two-thirds of America's population. "In the eastern United States, I don't think a study of this scale has been done before," Liu said.
The scientists used the time range between 2002 and 2004 as a base line for mortality, when 187 people died from heat-related illnesses. Running two different climate change scenarios, they looked forward 55 years and measured how frequently heat waves struck and then calculated how many additional fatalities they would cause. There is no standard definition for a heat wave, in terms of neither temperature nor duration, so researchers defined four heat-wave scenarios of their own.
By midcentury, heat waves in the eastern United States will cause an additional 1,403 deaths per year on average under one climate scenario and 3,556 fatalities annually in the other. Mortality was concentrated in Southern states and in coastal areas, except for Maine.
"What we found is not surprising, because you would expect that in a hotter environment, you would get more heat-related deaths," Liu said. He noted, however, that the calculations leave out many other factors, like deaths stemming from higher average temperatures instead of just sporadic heat extremes. "This is a very conservative estimate."
Adaptation: a 'big key'
"In general, this is an ambitious attempt to look at future effects across a wide geographic region," said Patrick Kinney, director of the Climate and Health Program at the Mailman School of Public Health at Columbia University, who was not involved in the research. "As with many other recent papers, it mainly highlights the possible increasing risk from heat under a changing climate."
However, uncertainty still swells around these projections.
"We do know that individuals that experience persistent exposure to extreme heat deal with it better," said George Luber, associate director for climate change at the National Center for Environmental Health at CDC. "Adaptation is a big, big key in here, but it's very difficult to model adaptation."
Another facet of health risk from heat waves is the physical environment people live in. "The differences in vulnerability vary from neighborhood to neighborhood," Luber said. Densely packed city centers lined with concrete and asphalt retain more heat than sprawling, leafy subdivisions with tree-lined boulevards, so how much heat afflicts you changes with your ZIP code.
CDC is aiming to avert some of the harm from heat waves, reaching out to local health departments and helping them identify the vulnerable, since the effects are highly localized (ClimateWire, June 7). Hospitals in Miami would barely notice any difference in admissions during a 90-degree-Fahrenheit stretch, but a sudden stretch at this temperature in Seattle might overwhelm local health resources. "Some communities will see this as a novel threat, and some will see this as an enhanced risk," Luber said.
Infrastructure like the electrical grid is another crucial target. "One of the critical challenges we're preparing for is the loss of primary adaptation -- that is, air conditioning -- during heat waves," Luber added.
Researchers are now gathering more heat and health data across the United States to inform their models, identifying specific temperature thresholds that produce elevated risk in a given region.
Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500.
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