A new study in PNAS identifies a natural feedback loop that stabilized Earth's climate for over 60 million years. Researchers found that changes in sea level control how much phosphate reaches the ocean, which in turn affects marine productivity and carbon burial in seabed sediments. When sea levels were high, less carbon was buried, leaving more CO2 in the atmosphere. When sea levels dropped, more carbon got stored, cooling the planet. The mechanism worked best when sea levels were 10 to 40 meters above today's levels. The authors say this could help improve models of how oceans respond to modern climate change. Scientists warn that a 4 degree Celsius rise by 2100 could bring extreme weather, wildfires, and ecosystem disruption. This is a relevant read for anyone tracking long-term carbon cycle dynamics and natural climate regulation. It does not offer immediate policy or market takeaways, but it adds context to how Earth's systems have kept temperatures in check over geological timescales.
