A few points to take note of:
1. Although the rhetoric about scientists’ “tossing out everything they thought they knew,” is over the top, it is an important reminder that scientific uncertainty goes both ways.
The deniers point to the uncertainty in scientific predictions to argue that we should do nothing. But scientific models might also be underestimating the actual dangers of climate change.
Indeed, given that science tends to be a fairly conservative enterprise (more evidence is demanded for claims of drastic changes), it might even be more likely that scientists will underestimate danger than overestimate it.
2. Starting at 3:45 there’s mention of the very important (but little discussed) point that as the arctic warms, the permafrost will melt and give off methane (which is a powerful greenhouse gas), which will lead to even more global warming. As the climate starts to change, we can expect it to continue to change, faster and faster.