And you’re skating awfully close to the ‘if something could be theoretically solved, that means it is already solved’. That is also not valid reasoning.
I’m pointing out that the scope and scale of the actual changes that need to happen is so large that it will require a lot of work to solve it, in practice. Without everyone (well, 90% probably) starving to death, anyway.
Should we be starting? Yes. But it will require actual concerted effort and significant tradeoffs. And a lot of time.
We’ve been working very hard to get to this point for a century now.
Now you're confusing "solvable" with "solved". Different concepts!
Of course a lot of work would be needed. The work, however, would be justified and very likely rewarded. There don't appear to be any showstoppers that would prevent it from succeeding.
The ultimate problem is one of collective action, internalizing costs that are now externalized. We've solved problems like this before, globally for example with the ban on CFCs. Here the costs and stakes are even higher.
Fossil fuel use will ultimately drive some countries near the equator to such levels of heating that life will become difficult or impossible. India and Pakistan have nuclear weapons, so they (particularly India, which has hydrogen bombs and a much larger economy) can threaten to kick over the global card table if the problem is not effectively addressed.