Agence France-Presse: With 19 months to go until the deadline for a new, global pact on climate change, the United States' top negotiator cautioned on Thursday against unrealistic expectations, saying the deal "won't be perfect"."It is important that our expectations be ambitious, and also grounded in reality," special envoy Todd Stern told journalists in Paris, where he met officials of the French government, who will host the 2015 meeting where the agreement must be signed."I'm sure it won't be perfect," he added. "This...