The United Nations will seek $800 million more in aid from the international community to respond to soaring life-saving needs of Pakistani flood survivors, a UN official said Friday. The unprecedented deluges — likely worsened by climate change — have killed 1,678 people in Pakistan since mid-June. About half a million survivors are still living in tents and makeshift shelters. Julien Harneis, the UN resident coordinator in Pakistan, told reporters in the Pakistani capital, Islamabad, that the latest appeal will be issued from Geneva on Tuesday. It comes just weeks after the agency sought $16…