Why? If people are not alarmed, they won't take the necessary extreme measures and extreme and global measures is what we all need.

People become desensitized to it, unfortunately.

Mostly policy is necessary though, and politicians love half-hearted efforts.

People just don't believe it, largely thanks to past alarmist warnings (like An Inconvenient Truth) that have already proven false.

What can you really call alarmism at this point, though? We passed 400 PPM in 2016. Even the best-case scenario is incredibly alarming.