Aerial photo shows a flock of sheep roaming along the Siling Lake in Naqu City, southwest China's Tibet Autonomous Region, April 29, 2020. The frozen surface of the plateau lake in Tibet is thawing with temperature rising up. (Xinhua/Tian Jinwen)

Sheep are seen by the Siling Lake in Naqu City, southwest China's Tibet Autonomous Region, April 29, 2020. The frozen surface of the plateau lake in Tibet is thawing with temperature rising up. (Xinhua/Hou Jie)

Photo taken on April 29, 2020 shows the scenery of Siling Lake in Naqu City, southwest China's Tibet Autonomous Region. The frozen surface of the plateau lake in Tibet is thawing with temperature rising up. (Xinhua/Hou Jie)

Aerial photo shows a flock of sheep roaming along the Siling Lake in Naqu City, southwest China's Tibet Autonomous Region, April 29, 2020. The frozen surface of the plateau lake in Tibet is thawing with temperature rising up. (Xinhua/Tian Jinwen)