Here's Bill McKibben speaking at an Occupy Wall Street "mic check," where the crowd repeats back everything he says and acts as a sort of human-powered amplifier.
The reason that it’s so great that we’re occupying Wall Street is because Wall Street has been occupying the atmosphere. That’s why we can never do anything about global warming. Exxon gets in the way. Goldman Sachs gets in the way. The whole fossil fuel industry gets in the way. The sky does not belong to Exxon. They cannot keep using it as a sewer into which to dump their carbon. If they do, we’ve got no future and nobody else on this planet has a future.