90% of professional motor-vehicle operators, retail workers, call center staff, radiologists, surgeons and other jobs can be unemployed due to the deployment of special purpose technologies whose development is well underway.
Some of those people, through the normal avenues of market-based resource distribution, will become plumbers, construction workers, and fill other-hard-to-automate roles in order to earn a living.
If the state institutes something like UBI, then still more of them will become artists, writers, community organizers and fill other roles that might earn them some money but would not on their own guarantee a full, stable income.
When global heating and sea-level rise create clear market incentives to rebuild the national infrastructure, those among the unemployed who are capable to work on that stuff will have a strong incentive to do so.
But for the state to, through a guaranteed jobs program, make effective use of 40-50% of the population in reconstructing national infrastructure as a response to global heating does not seem (to me) realistic. Are enough of those people capable of gaining the required skills for those kinds of projects? Where should they go and what should they do?