AFP: The UN climate change chief on Monday warned feuding countries they must immediately begin working towards a deal to combat global warming, as gridlocked talks resumed in China. The six-days of talks in the northern city of Tianjin are part of long-running efforts through the United Nations to secure a post-2012 treaty to limit global warming and avoid potential environmental catastrophes. The event is the first time that China, the world’s biggest source of greenhouse gases, …