Hot days or heat waves? Researchers debate how to count deaths from heat
By Vivian La, Science.
Excerpt: More than 47,000 Europeans died from heat-related causes last year, the warmest on record globally, a study published this month found. The number was surpassed only by the 60,000 Europeans who died of heat-related causes in 2022. Another study this month found that the toll in Europe could triple by the end of the century if Earth continues to warm to 3°C or 4°C degrees above preindustrial levels. The numbers, though shocking, almost certainly understate the toll of hot weather, worsened by global warming. But scientists aren’t sure how to do better. Some argue the best way to understand the impact of heat is to track how death rates vary with fluctuations in temperature, as the European studies did. But others say a truer measure is to rely on officially declared heat waves and count excess deaths—those above the expected number—each day. ...Proponents of using heat waves to measure how temperature increases those risks say these events are the deadliest, worst-case scenarios, so understanding them is paramount for preparedness. ...Counting deaths during heat waves also captures the cumulative health impact of multiple hot days in a row, a nuance that studies focused on daily temperatures can miss. But limiting the scope of studies to heat waves likely undercounts deaths because there is no universal definition of a heat wave, says epidemiologist Vijendra Ingole of the U.K. Office for National Statistics. Heat waves are declared when temperatures exceed the historical average in an area. However, because of climate change, a hot spell that would once have been considered a heat wave might not be today, he says—yet remains deadly....