'Unfortunately, there's an incredibly huge gap between "loss of coastal regions" and "Earth becomes a second Venus"' … maybe there's not. And that's part of the problem. Psychologically people perceive differences as "linear". It's part of how our brains are wired: to go from A to B draw a mental line and try to walk it at a constant speed. The greater the difference, the longer the line, thus the longer it takes to get from A to B. Hence the "huge gap" sentiment. But climate is not a linear system. Going from A to B could be a tiny step. Or oscillating, or dampening, or all sorts of funny things. Modelling of, for example, oceanic plankton (which gives more than 50% of the atmospheric oxygen) showed that the difference between "happy ~20% oxygen in the atmosphere" to "no oxygen ever again" is a small temperature change [1,2]. Non-linear systems are very hard. But they are fact, not fiction. That one last metric ton of CO2 could really be the difference between "life as usual" and "goodbye complex life on Earth". Communicating that fact is unfortunately even harder. Because people cannot perceive these changes, they're stuck in the linear mindset. And this worries me, because when we realize we need to really do something it's probably already far too late. If it isn't already (but in that case, science won't matter…I'd rather turn the page to "existential philosophy in the face of extinction").

To me it seems like simple risk management, even with a small probability the loss would be near infinite, whereas the loss of "doing something" is probably negligible. (carbon tax, energy transition, discouraging procreation, anti-consumerist lifestyle … probably all beneficial for humanity from a birds-eye view)

[1] http://www.wolfandwildlifestudies.com/downloads/oxygendeplet...

[2] https://link.springer.com/article/10.1007/s11538-015-0126-0