The record-breaking heat wave that gripped Europe last week is now heading northward, and scientists warn that it could cause an unprecedented melt of Greenland’s ice sheet. The U.N. said that this month alone Greenland lost 160 billion tons of surface ice. If the ice sheet melts entirely, it would raise global sea levels by almost 23 feet. Last month was the hottest June ever recorded on Earth, while July is on track to be the hottest month ever.