The Union of Concerned Scientists released a new report, "Killer Heat in the United States," on Tuesday, warning that, if carbon emissions continue at current levels, extreme heat days are expected to rise sharply in frequency and severity over the next few decades.
The UCS predicts that, by mid-century, the number of days with an average heat index (or "feels like" temperature) above 100 degrees Fahrenheit will double, and the number with a heat index over 105 degrees will quadruple. The report notes that an increase in extreme heat could impact the average U.S. resident more than any other effect of climate change, but it still poses the greatest risk for vulnerable populations, including homeless people and outdoor workers.
Exposure to extreme heat can cause illness and even death. When the heat index reaches 90 degrees, sun stroke, heat cramps, and heat exhaustion become risks, particularly for people who do physical work outdoors. Risks increase and become more serious for more people as the temperature rises; the National Weather Service suggests local heat advisory warnings when temperatures exceed 100 degrees and excessive heat warnings when temperatures rise above 105 degrees.
According to the report, construction workers account for a third of heat-related occupational deaths. Texas and Florida, the two states with the highest concentrations of construction workers, are expected to see an additional month's worth of days with a heat index above 90 degrees by mid-century, the report finds.
The UCS points out that, in the agriculture industry, migrant farmworkers in particular face barriers to preventing heat-related injuries: harsh working conditions, often a lack of health insurance, and, in some cases, immigration status.
Cities in general will face an unprecedented increase in intense heat, largely due to the "urban heat island effect," meaning characteristics of cities such as the lack of trees and abundance of heat-retaining materials like asphalt, cement, and pavement cause cities to be hotter than surrounding suburbs and rural areas. But within cities, the effects of intense heat disproportionally harm residents who are not white, who are experiencing poverty, or who are homeless, according to the report.
The researchers point out the 1995 Chicago heat wave, which led to more than 700 deaths, is "seen as not simply a natural disaster, but a societal one as well, with isolated, elderly African Americans suffering a disproportionate death toll because they were unable to flee overheated, non-air conditioned apartments."
Climate change and global warming contribute to other dangers, such as wildfires, that place outdoor workers and homeless people at heightened health risk when they breathe in smoke. Kate Wheeling and John Upton reported for Pacific Standard on the 2017 Southern California wildfires and their effects on vulnerable populations:
David Ewing wears a bright white dust mask, his face behind it puffy and red, as he sits on a stone bench in downtown Santa Barbara, California. A fine layer of ash covers the pavement at his feet, dirty residue from wildfires ravaging the region.
"When I woke up yesterday I couldn't breathe," says Ewing, who is homeless and has been diagnosed with cancer. He spent the previous night sleeping behind a Saks department store. "This stuff is just wiping me out."
Jack Herrera wrote for Pacific Standard about an organization's efforts to quell the impacts of wildfire smoke on farm workers in late 2018 by providing masks to wear while they continued to labor in the fields, even as public school students and others were told to stay home or indoors:
Even though California's labor laws call for employers to determine if conditions are too harmful for farmworkers to work, [Lucas] Zucker [of the Central Coast Alliance for a Sustainable Economy] says that state officials rarely travel to rural areas to enforce these protections. "Even though they have that guidance, there's essentially no teeth behind it," he says.
And climate change may be contributing to the opposite kind of weather as well: Emily Moon's story about the 2019 polar vortex in New England and the Midwest illustrates how the nearly 200,000 unsheltered people in the U.S. are in disproportionately great danger of health risks even in the winter. Some researchers suggest a recent increase or change in the pattern of these types of extreme cold weather events are linked to climate change in addition to extreme heat events.