If the main argument is economic costs, then this turns the discussion from a global to a localized problem, whether the required actions or sacrifices justify the local risks.

For example, is it worth for some country to "invest", say, $100 billion in reducing emissions - which, at least unilaterally, won't be sufficient to prevent the effects of climate change but just mitigate them - or can they achieve better mitigation by a comparable investment in reinforcing their shoreline, updating or relocating buildings, etc?

If USA had to vote on whether to spend (or lose by restricting growth) $1 trillion of USA resources to prevent $10 trillion of future losses in SE Asia, then I'd assume that such proposals would be swiftly declined; spending our resources on other things now and having someone else pay a huge price later would be considered a quite good deal by many governments, as the countries that most need to take action are not the same countries that will bear the harshest consequences.