A heat wave is raising temperatures to dangerous levels across much of Europe, just days after a heat wave in North America saw over 3,000 temperature records set. For more, we speak with climate scientist Michael Mann, who warns that heat domes and flooding have nearly tripled since the 1950s. "At some level, this isn't that complicated. You make the planet hotter, you're going to have more frequent and intense heat extremes," says Mann, a professor of environmental science at the University of Pennsylvania. Mann's upcoming book, co-authored with vaccine expert Dr. Peter Hotez, is "Science Under Siege: How to Fight the Five Most Powerful Forces That Threaten Our World."