Sweltering heat waves that typically strike once every 20 years could become yearly events across 60 percent of Earth's land surface by 2075, if human-produced greenhouse gas emissions continue unchecked.These are among the findings of a new study by Claudia Tebaldi of the National Center for Atm... Show moreSweltering heat waves that typically strike once every 20 years could become yearly events across 60 percent of Earth's land surface by 2075, if human-produced greenhouse gas emissions continue unchecked.These are among the findings of a new study by Claudia Tebaldi of the National Center for Atmospheric Research (NCAR) and Michael Wehner of the Lawrence Berkeley National Laboratory. Show less