Assume it is the year one billion

[james_davis_nicoll]

How can one maintain the Earth's ability to support complex life?

Comments

[armiphlage]

If you're starting from the surface, perhaps it might be more energy-efficient to float reflective junk in the oceans? Better yet, self-replicating junk?

Diatoms have long-lasting transparent silica frustules, that sink to the bottom of the ocean when they die. What if you genetically engineered diatoms to grow opaque, pore-free frustules? Entrapped air would let them float, covering the ocean with a reflective scum. This would counteract increased solar flux, while also reducing evaporation of the oceans.