U.S. officials say Secretary of State Hillary Rodham Clinton plans to name a special envoy for climate change. Clinton has picked Todd Stern, a former White House assistant who was the chief U.S. negotiator at the Kyoto Protocol talks in her husband's administration, the officials said Monday. They spoke on condition of anonymity ahead of a planned midday State Department ceremony where Clinton will announce the appointment.Stern served in the Clinton administration from 1993 to 2001, first in the White House, where he worked on the Kyoto Protocol and coordinated the president's Initiative on Global Climate Change and then at Treasury, where he was a senior adviser to the secretary.