SYDNEY, Sept. 6 – One of the first agreements to emerge Wednesday from meetings between President Bush and Australian Prime Minister John Howard was a pledge to take joint action to combat climate change. It is an issue that neither leader has been closely associated with in the past. Both Australia and the United States refused to ratify the Kyoto Protocol, the 1997 U.N.-led effort that set goals for major industrialized nations to cut the greenhouse gas emissions that cause global warming.