By Valerie Volcovici and David Stanway WASHINGTON (Reuters) – The U.S. and China have delivered big wins in climate diplomacy through the unique relationship of their chief climate envoys, but the two countries are bracing for change as the Chinese envoy retires and the U.S. readies for an election. In an interview with Reuters, U.S. Special Climate Envoy John Kerry was vague about his plans for the future. “No matter what, I am going to try to do what works best,” he said after last week’s U.N. climate summit, COP28, in Dubai. “I haven’t made any decisions about anything, and I will continue …