Despite promises, California doesn’t know how many people died in record summer heat wave
The heat wave of 2015 may have killed as many people as the record fire season of 2014.
As climate change makes heat waves more common, it’s getting harder to determine who died from the high temperatures, a new analysis of records from every state in the union shows.
That’s because the number of deaths reported to the state and federal government in each year is often a few days behind the actual number of deaths.
For example, in 2015, when the heat wave hit California, there were 612 confirmed deaths in the Golden State, but the government only accounted for 584. The problem is likely even more pronounced in other states. It’s difficult to determine because of the difficulty of calculating deaths and because many people die from heat when they’re already seriously ill — not when they’re trapped in a heatwave.
“This is a problem in all the states,” says Jonathan Overpeck, a research professor at North Carolina State.
In New York City, the health department reported there were no deaths during the heat wave of 2015, but that figure was based on an unofficial calculation. It seems the city’s counting methods are still being studied, he says.
The problem is particularly high in the Midwest, says John Nield, a professor of environmental epidemiology who studies heat and mortality. States such as Ohio and Pennsylvania report zero deaths — even though the temperatures they’re experiencing on average are higher than what was reported in 2015.
California’s problem is in part because it has a unique way of counting deaths: It’s not unusual for a death to be reported on the day it happens. That makes it difficult to figure out the real number of deaths because some people die with symptoms before their deaths are reported.
Heat waves are becoming more common in the U.S.
As the Earth warms, heat waves become more common and longer. A study published last year in the Proceedings of the National Academy of Sciences said the future is “all but guaranteed” that U.S. cities will experience heat waves, especially in the summer.
In 2015, there were heat waves in Texas, Nevada, Oklahoma, Arizona,