Describe the role of oceans in the reduction of carbon dioxide levels in the atmosphere.

The oceans played a crucial role in reducing carbon dioxide levels by absorbing it from the atmosphere. As the Earth cooled, water vapour condensed to form oceans, which then dissolved carbon dioxide, leading to a decrease in its concentration in the atmosphere.

A strong answer should directly address the approved learning objective to explain that carbon dioxide dissolved in the oceans as the atmosphere changed. This question belongs to How carbon dioxide decreased within The composition and evolution of the Earth's atmosphere, so the response should use that exact curriculum context rather than a generic statement. The answer is correct when it names the key idea, explains the link to carbon dioxide, and keeps the wording specific to AQA GCSE revision.