Not doing anything has a certainty of turning the ocean to a mild acid, with disastrous effects that are already becoming visible in coral bleaching and shellfish die offs. And carbon that is already in the atmosphere and not yet dissolved is only going to make it worse.
We are at the point of choosing between what disasters we will suffer, rather than figuring out how to not have a disaster.
Why are we so concerned about ocean acidification from CO2, when past CO2 levels were far higher than now and all of the shellfish species that currently exist lived back then too? Wouldn't it be a good idea to consider the massive quantities of known toxins we pump into the oceans rather than fixating on a red herring?
Your question assumes that the oceans had to have been acidic because CO2 was high. This assumption is wrong.
You don't get acidification as long as CO2 levels change slowly enough that it mixes down to the bottom of the ocean and then gets buffered by calcium bicarbonate being dissolved there and mixing back to the top. But this mixing takes place on the scale of a thousand years. This is no big deal for CO2 level changes taking place over geological time. But it doesn't help shellfish with sudden increases of CO2 taking place on a scale of decades or centuries.
Another geo-engineering idea is to speed up this mixing by pumping air deep down into the oceans. Personally (as a PhD geoscientist), I think that taking CO2 out of the air, compressing it to a liquid, and re-injecting it back into the geologic formations that the oil came from in the first place, is the procedure for getting rid of CO2 that is least likely to screw things up even more. It would just go back where it came from (many caveats, but basically can work).
Start raising a tax on CO2 emissions and at the same time start paying people to put it in the ground. Raise the price on both each year and you could reach equilibrium pretty fast. Should have started 20 years ago, but now is better than never. Maybe start at increasing it at $10 dollars a ton/year. $10/ton is about $4 per barrel of oil. If people saw that sequestering CO2 would pay $100 a ton in a decade the research and excitement around the ideas would be huge and likely encourage many breakthroughs. Isolated solar and wind farms extracting CO2 from the air and pumping it underground could be a huge business.
You can say that if you like, but I tend to err on the side of scientific evidence. Even the hysterians most scary claims merely suggest that we "are headed for" ocean PH levels that are "unheard of in 25 million years". And yet the shellfish people are trying to tell us will die from slightly thinner shells have been around for a couple of hundred million years.
> Bivalves grown under near preindustrial CO2 levels displayed thicker, more robust shells than individuals grown at present CO2 concentrations, whereas bivalves exposed to CO2 levels expected later this century had shells that were malformed and eroded. These results suggest that the ocean acidification that has occurred during the past two centuries may be inhibiting the development and survival of larval shellfish and contributing to global declines of some bivalve populations.
i'm not sure where the claim "all of the shellfish species that currently exist lived back then too" is coming from, although it is correct that CO2 was higher in the past (https://www.skepticalscience.com/co2-higher-in-past.htm)
Look at the study, not just the summary. What does "preindustrial levels" mean? Preindustrial includes over 4 billion years, including years with no life on earth. It includes the absolute highest and absolute lowest levels of atmospheric CO2 ever in the history of the planet. They chose a very low level that would give them the biggest results, and compared it to a hypothetical future level which isn't actually possible to achieve because there's not enough carbon stored in all the fossil fuels on the planet to get close to it if we burned every drop. Yes, record low atmospheric CO2 means shellfish have slightly thicker shells. Does that have an actual benefit for shellfish, much less entire global ecology? Those low CO2 levels are unquestionably bad for other things, like plants, and humans. Shellfish survived previous high CO2 levels just fine, we have the fossils, they existed. They can go ahead and have slightly thinner shells, while we have more plants and more food.
Also, we're talking about coral bleaching and it being blamed on CO2 despite absolutely no evidence, and despite the fact that some coral reefs are seeing normal growth, while others which are in major pollution streams from Asian rivers are seeing bleaching events. But it has to be CO2 because Al Gore says so! Ignore the billions of tons of toxic waste being pumped into the Ocean by China and India and Africa! Europeans and North Americans are the problem with their evil CO2! They need to become poor like everyone else to save the planet!
We are at the point of choosing between what disasters we will suffer, rather than figuring out how to not have a disaster.