Sixteen-year-old Swedish climate activist Greta Thunberg has set sail for Europe, ending an 11-week visit to North America that saw her lead student strikes for the climate while calling out world leaders over their inaction on the climate crisis. Thunberg hopes to reach Madrid, Spain, in time for a United Nations climate summit in early December. She and her father Svante are sailing aboard the 48-foot catamaran, La Vagabonde, refusing to fly because of the high carbon footprint of air travel.