Great question! My work focuses in climate change and how it affects the ocean, so for me the answer is very clear: reduce the emissions of carbon dioxide (CO2).
Global warming is mainly caused by gases in the atmosphere, like CO2, trapping the heat from Sun. Most of the CO2 we produce does not go to the atmosphere though, around 85% goes to the ocean! So the ocean is basically saving our assess at the moment, but not for long: an excess of carbon in the ocean makes the water more acidic and puts marine life in danger, that’s exactly what we are seeing right now. No marine life = no carbon capture in the ocean = all carbon goes to the atmosphere = Earth warms enormously. Not a pretty picture.