Thousands of Americans are expected to perish in cities during future heat waves

Heat waves kill more Americans than any other weather event. 
The torrid episodes are especially problematic in cities, where the concrete and asphalt sprawl traps heat, boosting already unusually hot temperatures by some 2 to 5 degrees Fahrenheit. 
Yet, as average temperatures continue their relentless rise, the U.S. government expects urban dwellers to experience more heat extremes, some unprecedented. Scientists, however, found that limiting Earth's warming this century to 2.7 degre