When we marched against the Iraq war, the demands were fairly simple even if they were ignored.
But when we march against "Climate Change" what are we asking for? What do we want to happen next?
http://peoplesclimate.org/global/#map
I suspect marching about climate change is like dancing about architecture. But if it makes us feel better, maybe it's still worth while.
http://www.theguardian.com/environment/live/2014/sep/21/peoples-climate-march-live