Scientists Solve a 66-Million-Year-Old Climate Mystery That Changed Earth Forever

An article from SciTechDaily reports on new research that helps solve a long-standing climate mystery: why Earth transitioned from an extremely warm “greenhouse” planet after the age of dinosaurs to the relatively much cooler, ice-capped world we know today .

The piece explains that scientists have identified a slow but powerful driver of Earth’s long-term cooling over the past 66 million years—changes in the chemistry of the oceans. By analyzing fossilized remains of tiny marine organisms, known as foraminifera, researchers reconstructed ancient seawater chemistry and found that calcium levels in the oceans have declined by more than 50 percent since the early Cenozoic Era. This shift mattered because seawater calcium plays a key role in how carbon moves between the ocean and the atmosphere. When calcium levels were high, the oceans released more carbon dioxide into the air, strengthening the greenhouse effect. As calcium levels gradually fell, more carbon dioxide was pulled out of the atmosphere and locked into marine sediments, weakening the greenhouse effect and allowing global temperatures to drop by as much as 15 to 20 degrees Celsius. Understanding this process is important today because it highlights how deep Earth and ocean processes can shape climate over geological timescales, offering context for how carbon cycling influences long-term climate change.

Yair Rosenthal, RCEI Affiliate and professor at Rutgers University, was a co-author on the study and contributed key insights linking ocean chemistry to deep Earth processes. Rosenthal explained that the decline in ocean calcium closely tracked a slowdown in seafloor spreading—the volcanic process that creates new ocean crust. As this process slowed, the chemical exchange between newly formed rocks and seawater changed, leading to lower calcium concentrations in the oceans. As Rosenthal put it,

“Seawater chemistry is typically viewed as something that responds to other factors that lead to changes in our climate, rather than being the cause itself.” He added that the team’s findings suggest a shift in perspective is needed, noting, “Our new evidence suggests that we must look to changing seawater chemistry to understand our planet’s climate history.”

Rosenthal’s contribution is central to the story; he frames ocean chemistry not as a passive background player, but as an active driver of some of Earth’s largest climate shifts.

Read the full article here.