With at least 49 confirmed hyperthermia deaths, 2010 has already been the deadliest year on record. That fact is surprising for some safety advocates, since awareness of the issue has gone up significantly in the past few years.
To get some answers, I called Jan Null, a meteorologist at the San Francisco-based Golden Gate Weather Service and the world's foremost scientific expert on hyperthermia deaths.
Null, who began researching the issue in 2001, keeps perhaps the most extensive database of incidents across the country. He's also testified as an expert witness in several criminal cases. This year's 49 confirmed deaths -- authorities are still investigating incidents in Louisiana and Iowa, Null says, and that number could still go up -- surpasses the previous high of 47 in 2008. This is the highest number since safety experts warned parents to move child seats to the back of the car in the early '90s. Before then, Null says, there were fewer than ten a year nationwide.
So, why so many this year?
Null says it doesn't necessarily have anything to do with global warming. "I wouldn't lean toward it being a warmer summer necessarily," he says. "If you leave a child in a car for three hours, it's not going to matter if it's an 80-degree day or a 100-degree day."
Null was one of the first scientists to study the specifics of just how fast the inside of vehicles heat up in sunlight. The temperature inside a car can go up 40 degrees in an hour, making young children particularly vulnerable when left for longer than even five minutes. (Janette Fennell of KidsandCars.org stresses parents should never leave a child alone in a car for any amount of time for any reason.)
In the eastern part of the country, this was a hotter-than-usual summer. But in some places where temperatures were warmer -- South Florida, for example -- there were actually fewer deaths than in years past. (This year, Florida has had at least six deaths, but in 2004, a cooler year, Veronika Balta was the first of ten children to die in the Sunshine State.)
Climate change might account for a degree or two more in a mean temperature, Null says, but that wouldn't have a large effect on the rate of hyperthermia deaths.
One theory is the economy: Perhaps parents are working more.
"That could certainly be a factor," says Null, "People are worried about unemployment, losing a job, working more, maybe. But are people that much more distracted because they're worried about jobs this year compared to last year?" Last year, there were 33 deaths nationwide, nearly a third fewer than this year.
Null points out that in his records, there's never been a case of a parent intentionally doing this to murder a child (though that was the plot of an episode of CSI). About half the cases involve a parent getting distracted and simply forgetting a child is in the car. In other cases, the child crawls into the car without a caregiver knowing.
Has awareness of this complicated issue actually had a negative effect somehow? Is it just a rise in overall population? Are memories just getting worse?
None of those things, even if true (and there's no evidence to suggest that), are likely to explain a shift in numbers like this, Null says.
The truth is, with about 500 deaths on record since 1998, the sample size is just not large enough for a statistically significant study. At this point, there's no scientific way of knowing why this year has been so deadly.
"There are lots of little reasons but no primary factor," Null says. "I'd have to chalk it up to a statistical anamoly."