Senator John Kerry arrived at the United Nations climate conference here on Thursday and immediately reassured delegates that the United States would take strong measures to combat climate change.“President Obama will be like night and day compared to President Bush，” Mr. Kerry， Democrat of Massachusetts， said at a news conference， adding， “Congress and the president-elect are committed to movement on mandatory goals as rapidly as possible.”

　　Although the incoming president has no official representatives here， the conference center is crawling with Congressional representatives and their staff members， a sign of the political transition in the United States.