EcoWatch: The New York state elections just concluded, and the national midterms are still weeks away, but there is a campaign office in downtown Manhattan that has just gone into overdrive. Volunteers there are hard at work on another deadline: Sept. 21. That’s the day of the People’s Climate March, what promises to be the largest demonstration for action on climate change in world history. The march has brought together more than 1,100 organizations at last count, from the New York City Environmental Justice…