Is It Too Late?
The oceans can't recover from the heat trap of carbon-dioxide as quickly as the atmosphere could.
The rise in temperatures in the ocean work on a mean turnover rate of up to 1000 years, so even if all carbon-based energy extraction were to cease right now, it is probably too late to prevent a rise in temperatures to levels mortal to coral reefs. Corals lay the foundation for underwater colonies of marine life. If the coral die out, the effects run straight up the food chain to the fish that humans depend on for food. Unless we find a way to assist the coral to recover, we will reduce the available food stock for humans from the sea.
It is even now close to the breaking point from overfishing, and left to herself to recover the ocean may simply say "Give me more time, you fools!" Perhaps there is a way for humans to undo the damage we have caused and allow our foodstocks to return to sustainable levels.
Bio-Rock Mineral Accretion Technology may be one way that we can put things back to rights (we still need to reduce our carbon-dependence:)
Biorock Technology, or mineral accretion technology is a method that applies safe, low voltage electrical currents through seawater, causing dissolved minerals to crystallize on structures, growing into a white limestone similar to that which naturally makes up coral reefs and tropical white sand beaches. This material has a strength similar to concrete. It can be used to make robust artificial reefs on which corals grow at very rapid rates. The change in the environment produced by electrical currents accelerates formation and growth of both chemical limestone rock and the skeletons of corals and other shell-bearing organisms.
It's a possibility, and I think one worth exploring.