However, assume it did. Then ocean acidification is still a first world problem. If you're the government of a developing country (India, China, Brazil, ...) where most people don't even have reliable electricity, and you get to choose between washing machines for your people and a more basic ocean, you go for the washing machines. And you will burn gigatons of coal to enable those washing machines.

Globally speaking, government action will not work, because most governments don't care (for good reasons, arguably). On top of that, international agreements are mostly concerned with non-solutions like a reduction of carbon emission by some irrelevant fraction by a time when it's too late (like 50% by 2050 or some such nonsense). Even if the first world managed to do that, the growth of the developing countries annihilates any such progress within a decade. And even if the whole world was on board and reduced global emissions by 50%, we'd just fuck up the planet half as quickly, but every bit as reliably. The reality is that if global climate change really is such a big problem, we need to get to zero carbon emissions, actually negative carbon emissions, fairly quickly.

Your dream of a world police enforcing zero carbon emissions collides with the reality that they (the UN or whoever else is closest to a "world government") aren't even trying, and that they don't actually have an alternative plan.

Perhaps the most encouraging trend is the exponential growth of the photovoltaic solar panel industry. If that continues, it will certainly be a huge help. But you have to weigh that against the fact that there are still a couple of billion people with no access to power at all. All together, world carbon emissions are not likely to fall anytime soon.