Bloomberg: Australia, the world’s biggest coal exporter, will push the U.S. and China to show more "ambition" in this year’s global warming talks, Climate Change Minister Penny Wong said. We will "use our relationship with key nations to encourage political will and to encourage more ambition in the agreement," Wong said in an interview in Sydney on July 31. China, the U.S. and India are "key" to success, she said. China and the U.S., the world’s largest polluters, have yet to commit to …