It seems clear to me that the problem of maintaining a reasonably steady temperature and sea level is real enough (at least to some significant degree).
Human induced warming is definitely a strong possibility, but the climate stability of the last 10,000 years is extremely unusual over the last few million years.
Thus we need to look at systems that give us the ability to manage the entire system.
Such systems cannot be manufactured with linear technology, we need exponential tech.
For reasons of the energy demands and the waste energy produced, any seriously large scale use of such exponential technology needs to be done off planet, and the results of such manufacturing returned to earth if required.
That requires fully automated mining/manufacturing systems, which are not quite yet a reality, but could be very close if it becomes a societal priority.
One other side effect of such technology would be universal and radical abundance of most goods and services (which does break all economic systems dependent upon markets, as market measures of value are all predicated upon scarcity – even Hayek acknowledged that much).
That does raise serious issues about how does one maintain security and cooperation when markets and trade are no longer present (with all their functions of distributed governance, distributed risk management, distributed network formation, distributed trust networks, etc).
All solvable, and a seriously non-trivial problems space.
Understanding the sorts of solutions that are possible requires understanding that all complex life forms (and any meaningful construct of freedom) are predicated on cooperation. That is not yet a common understanding of the evolutionary process. Most people are still under the illusions that evolution is all about competition, whereas in reality, competitive environments always tend to drive systems to some set of local minima on the complexity landscape (ie remove freedom, and limit diversity).