One of my favorite tropes — used by activists of all stripes— is ‘acting like a rock in a stream’. According to this metaphor a handful of people could become a catalyst for change, simple by standing firm. (An act often taken quite literally, like demonstrators gluing themselves to the road or large immovable objects). The idea is that after attracting a number of like-minded people, together they could create a tipping point, beyond which history would be forced to change its course — not unlike a river, after having a large enough number of rocks thrown into it. Now take a look at the chart below, depicting an exponential rise in atmospheric CO2 concentrations, and see if the metaphor has earned a merit.