FILE - In this Friday, June 26, 2015 file photo, mourners attend a funeral for unclaimed people who died of extreme weather, in Karachi, Pakistan, after a devastating heat wave that struck southern Pakistan the previous weekend, with over 800 confirmed deaths according to a senior health official. A study published in Nature Climate Change on Monday, May 31, 2021, has calculated that more than one-third of global heat deaths can directly be attributed to human-caused climate change.