Once again, the world is on a sprint toward a new agreement on global climate change. The last time this happened — in 2009 — the sprint ended in acrimony in Copenhagen. This time, the signs are more auspicious. As someone who has been writing for nearly 25 years about the difficulties of making serious progress on climate change, I am more optimistic today than I have been in a very long time. When governments gather in Paris late this year, I believe they are likely to adopt a watershed strategy for slowing climate change.  I’m optimistic for two reasons. First, the logic of Paris is new. In the past, governments have tried to negotiate single, massive, and integrated A shift in strategy was evident at climate talks in Lima in December, where Peru’s Manuel Pulgar served as conference president.