Earth's climate regulation over 60 million years: How sea level and ocean phosphate control carbon dioxide

A new study published in the Proceedings of the National Academy of Sciences reveals that Earth has a natural climate regulation system driven by sea level changes and ocean phosphate levels. Over the past 60 million years, shifts in sea level altered the amount of phosphate in the ocean, which in turn influenced marine biological activity and the drawdown of carbon dioxide from the atmosphere. This feedback loop helped keep the planet's climate within a range suitable for life, despite major warming and cooling events. The research, co-authored by Zunli Lu, professor of Earth sciences, provides a concrete mechanism for Earth's long-term climate stability. It shows that when sea levels dropped, less phosphate reached the ocean, reducing carbon uptake by marine organisms. When sea levels rose, more phosphate entered the ocean, boosting carbon sequestration. This finding matters for understanding natural carbon cycles and could inform how we think about ocean-based carbon removal strategies today. For those tracking climate policy and carbon markets, this study reinforces the importance of ocean chemistry in the global carbon budget. It highlights that natural feedbacks operate on geological timescales, but human emissions are overwhelming them now. The work adds to the case for protecting marine ecosystems that play a role in carbon storage, such as coastal wetlands and phytoplankton blooms.