The Warming was a period of time in Ocampan history in which Ocampa's surface became a total desert around 500 Ocampan generations ago due to the Nacene. The Caretaker came to protect the Ocampa. He opened a chasm and led them to a location where, after the Warming, he designed and built a city where they could live. The story of The Warming was told to Harry Kim and B'Elanna Torres by an Ocampan doctor. It was also told to Kathryn Janeway and Tuvok by the Caretaker himself. (VOY: "Caretaker")