U.S. formally embraces Copenhagen climate deal Photo 4:24pm EST WASHINGTON (Reuters) - The United States on Thursday formally notified the United Nations that it has embraced the Copenhagen Accord setting nonbinding goals for reducing greenhouse gas emissions that was negotiated last month. Todd Stern, the top U.S. climate negotiator for the Obama administration, also gave notice that, as expected, it will aim for a 17 percent reduction in emissions of carbon dioxide and other gases blamed for global warming by 2020, with 2005 as the base year.