Naomi Seibt, a blonde German teenager, has become a U.S. think tank’s weapon of choice when it comes to combatting climate activist and global phenomenon Greta Thunberg. The Heartland Institute, a conservative think tank that rejects the scientific consensus on climate change, labeled Seibt as “a fantastic voice for free markets and for climate realism” and has booked her to speak at CPAC later this week. Seibt has already headlined at the UN climate conference in Madrid this past December, and CPAC will be her American debut. Although the German 19-year-old rejects “climate alarmism,” she mimics Thunberg in several ways,...