Reuters: The United States promised on Tuesday to take “ambitious actions” under a new U.N. pact to fight global warming and urged a dramatic increase in cash to help developing nations cope with climate change. A submission to the United Nations outlining Washington’s ideas for a treaty due to be agreed in Copenhagen in December also said many nations should outline greenhouse gas cuts both for a mid-term goal of 2020 and a long-term 2050 target. “The United States is committed to …