President Barack Obama said charts and graphs he’s seen detailing the effects of climate change on Earth are “terrifying.”

In an interview with The New York Times, Obama outlined his worries about climate change and how people might perceive the global issue.

“What makes climate change difficult is that it is not an instantaneous, catastrophic event,” Obama said. “It’s a slow-moving issue that, on a day-to-day basis, people don’t experience and don’t see.”

Obama visited the remote Midway Atoll last week as part of a push for more environmental protections. He also announced $40 million in programs to help island nations and other communities vulnerable to climate change.

SAUL LOEB/AFP/Getty Images Obama tours Midway Atoll on Sept. 1, 2016. The coral reef is one of the most remote places on the planet.

Obama has repeatedly warned against the harmful effects of climate change, saying it is a threat to the U.S. military and national security. In a 2015 speech, Obama repeatedly said “we’re not moving fast enough” to combat the damage caused by a warming climate, warning that “we will condemn our children to a planet beyond their capacity to repair.”