"The small contribution we’re trying to make is to nationalize this so it's not just an issue for those whose back yards it is going through or for indigenous people whose ancestral lands are being ripped apart."

Calling All Baby Boomers

McKibben, a veteran organizer of massive exercises, could assume the title of Pied Piper when it comes to prompting sweeping action on climate change.

His large-scale activism began in 2007 — the year before he launched 350.org — with a Step It Up campaign featuring gatherings in all 50 states. Follow-up work parties and political rallies expanded from 5,200 events in 181 countries in autumn of 2009 to 7,400 events in 188 countries last October. After last November’s midterm elections, he coordinated a satellite-broadcast, planetary art show titled 350 EARTH.

Organizers are emphasizing that such "serious stuff" near the White House requires a peaceful demonstration, not a smash-up. Environmental and democracy campaigns will be offering nonviolence training beforehand.

The Middlebury College professor knows the August event will be a magnet for students. But he wants to see plenty of gray hair at the protest, too, because it's "past time for elders to behave like elders."

"It's incumbent on those who have spent our whole lives spewing carbon into the atmosphere to do something about it," McKibben concluded. "Most had interesting first acts in their lives that involved the civil rights and anti-war movements. That was before becoming preoccupied with other activities, mainly consuming things.

"Now, they're ready for a different kind of third act. Perhaps this will give them a chance to get back to their idealistic roots."