Excerpts from Books and Wikipedia
"A June 2017 analysis in Nature Climate Change, 'Global Risk of Deadly Heat,' examined studies of 'lethal heat events' published in the last quarter century. The researchers found that, absent strong climate action, we are headed toward levels of warming by 2100 that will expose as much as three fourths of the world’s population to a deadly combination of temperature and humidity for at least 20 days a year." [Romm, p. 109]