U.N. Secretary-General Ban Ki-moon traveled to Antarctica on Friday and called for urgent political action to tackle global warming. He spoke during a tour of three scientific bases on the Antarctic continent, where temperatures are their highest in about 1,800 years.

Ban Ki-moon: “Again, I was told by the scientist that entire western Antarctica is now floating. This is one-fifth of a total continent, size of this total continent. If it broke up, the sea level rise — sea level may rise as much as six meters, 18 feet. This is very alarming.”

It was the first visit by a U.N. chief to Antarctica.