Hi Carola,
I'll give it a try. Others will hopefully fill in anything I miss. The gist of the argument is "what's the worst that could happen?". Basically, the guy in the video presents 4 scenarios and their consequences.
1. Global warming turns out to not be real problem and yet we end up taking action against it. Worst possible consequence: wasted money and damaged economy, possibly economic recession/depression.
2. Global warming turns out to not be a real problem and we take no action against it. No bad consequence.
3. Global warming turns out to be a real problem and we take action against it. Consequence: we have spent money and made sacrifices, but we have done all we could to lessen the damage and it turned out to be a good decision.
4. Global warming turns out to be a real problem and we have taken no action against it. Consequences: global economic, political, health, and environmental catastrophe.
His argument is that we have to choose what to do based on risk/benefit. Basically, regardless of what happens, we risk too much by taking no action. Even if global warming turns out to not be a problem, we are gambling our entire planet by not taking it seriously.
He does a much better job explaining this! I hope I did it justice.
Amy