Passage Summary: An oceanographer proposes hiding carbon dioxide in the deep sea, arguing that because the water down there doesn't move to the surface very often, the gas will stay stuck there for a long time.

Conclusion: Pumping carbon dioxide into the deep ocean is an effective strategy for significantly lowering atmospheric carbon dioxide levels.

Reasoning: Deep ocean water is dense and cold, taking hundreds of years to mix with surface water, which would keep any dissolved carbon dioxide trapped far below the surface for centuries.

Analysis: The argument assumes that the only way for the carbon dioxide to escape is through the natural mixing of water layers. To bridge the gap, the oceanographer must believe that the carbon dioxide won't find another way out, such as bubbling up or reacting in a way that releases it back into the atmosphere. Look for an answer that rules out a potential 'leak' in this storage plan. If the gas could escape even without the water mixing, the whole plan to 'trap' it falls apart.