Scientists extracted ancient air trapped in Antarctic ice to solve a 3-million-year climate puzzle. They measured tiny amounts of carbon dioxide and methane preserved in the ice and discovered something unexpected: greenhouse gas levels rose only modestly during a period when Earth's climate cooled substantially, particularly in the oceans.
This mismatch reveals that greenhouse gases alone did not drive the planet's long-term cooling. Instead, other mechanisms took the lead. Shifting ice sheets altered Earth's surface, ocean circulation patterns redistributed heat around the globe, and changes in reflectivity affected how much solar energy the planet absorbed.
The findings reshape our understanding of how climate systems work over millions of years. They show that multiple forces interact to reshape climate, not just the greenhouse gases scientists often focus on today. Researchers plan to continue analyzing ancient ice samples to map these interactions across different time periods. This work helps establish a baseline for natural climate variability, which scientists need to distinguish from human-driven warming occurring now.