Dangerous Humid Heat Days More Than Double Worldwide: Study

New York, July 13 (Jiji Press)–The average annual number of dangerous humid heat days in locations across the world more than doubled from 10 to 23 over the past 50 years, due chiefly to human-caused climate change, according to a recent analysis by U.S. research institute Climate Central. In Japan, the number of dangerous humid heat days, characterized by high temperatures and humidity that increase the risk of health issues such as heatstroke, climbed from 17 to 40 per year. In the analysis, the institute defines dangerous humid heat days as days when the daily maximum wet-bulb temperature, which reflects both temperature and humidity, reaches 25 degrees Celsius or higher. This is equivalent to a temperature of 25 degrees with 100 pct humidity. The same condition can also occur when the temperature is 35 degrees and the humidity stands at 44 pct because higher temperatures require lower humidity to produce the same wet-bulb temperature. The study compared the annual average number of such days recorded in the 1970s with that in the 10-year period through 2025. While the number of dangerous humid heat days is particularly high in Southeast Asia, it is increasing worldwide. In the United States, the annual average number of such days rose from 10 to 21. The figure increased from 41 to 53 in China and from 101 to 141 in India. In addition to the 254 countries, regions and remote islands covered in the study, 961 cities were examined separately. Among Japan’s 12 major cities, Fukuoka in the southwest recorded the highest number of dangerous humid heat days, with the annual number increasing from 35 to 59. The northern city of Sapporo recorded the lowest number, with the annual figure increasing from zero to one. “When heat and humidity combine and reach a certain threshold, your body can no longer sweat efficiently to cool you down, and that’s when things get dangerous for your health,” an official of the institute said. As global warming advances, humid heat days are likely to occur more frequently, potentially increasing health risks, the official added. END [Copyright The Jiji Press, Ltd.]