The reason for inaction has a lot less to do with the debate over why climate change is happening than it does the costs of actually stopping it.

The main problem is that since the burning of non-renewable resources creates the literal highest probability of keeping the current world population alive, deciding not to do that any more because it slightly increases global temperatures would be incredibly short sighted and kill a lot of people. The consequences of reducing global consumption on that scale would be disastrous for a lot of people to the extent that they would die, while the consequences for rising sea levels generally only force people to move.

Then couple that with the fact that there is definitely some % chance (maybe it's only 10%) that humans are NOT actually causing climate change, and such actions would end up killing a lot of people for no reason. Too many people get hung up on this idea that climate change deniers or man made climate change deniers are holding up some sort of sweeping global government action to prevent future disaster, but the reality is that the steps necessary for stopping something that is likely as uneventful as a slow rise in sea levels will definitely cost a lot of people their lives.