In an ideal world, we would reach net zero in time to prevent that. This is the only long-term solution. But what if, in a decade or two, every projection says we won’t? Are we to chastise the rest of humanity, say “you could have prevented this the proper way!”, and let the dominos begin to fall?
Geoengineering, if the science is proven, should only act as a last resort to prevent such a domino effect. It would symbolise a profound failure of our species. But surely, if we realise we failed, this risky Hail Mary is better than not acting?
The risks of another massive human intervention into the atmosphere are obvious. Furthermore, geoengineering risks giving many nations an excuse to keep burning fossil fuels. Nobody has the right answers yet and everybody sensible agrees we need to do everything we can to reach net zero first.
But what if we don’t?
It is of course possible that both technological and social approaches will prove insufficient, and we'll go well beyond the "safe" level of global warming.
Ed. this produces carbonic acid, but if you feed it slowly into the biosphere, small friends will turn it into bone and shell
Since global warming is trivially abated by aerosolizing seawater it would be negligent to revamp our economy and degrade our quality of life to avoid carbon emissions [which in this hypothetical the main negative is trivially abated].
But I’ll add - cloud seeding might prevent heating, but it can’t prevent ocean acidification. Secondly, if one country or organisation came to dominate it, and the world settled into a rhythm of pumping more carbon dioxide into the atmosphere and artificially mitigating the heating effects… what happens if the political winds changed direction for even a few years? We’d potentially see centuries of heating in a short timespan.
Just look at Europe’s reliance on the US (through NATO) for protection and the efforts to become more independent now that a Trump presidency has opened their eyes to the risk that carries. Further fossil fuel burning would mean more and more geoengineering each year, putting control in the hands of fewer and fewer nations. One benefit of most suggested geoengineering efforts is that the particulates fall after a few years. If we came to depend on it (we shouldn’t!), that constant maintenance should terrify us.
It’s an imperfect, short-term solution that could sentence future generations to horrific consequences.
At that point we'll probably have much worse problems.