Ethan I. Shedley’s 1979 Earth Ship and Star Song is a stand-alone science fiction novel. It was his debut novel.
Thanks to concerted efforts by many generations of humans, 21st Century Earth is clearly doomed to horrific death due to runaway greenhouse effect. When closely examined, every proposed mitigating technology has secondary effects that will accelerate the planet’s doom. Of the four possible coping mechanisms, three can be eliminated as impractical.
The best chance for the human race (and a selection of terrestrial lifeforms) is to flee the planet in great arks. The technology needed is in hand … save for one small detail.