Ice core study casts doubt over role of greenhouse gases in ancient climate shifts

A recently circulated commentary on new ice core research has reignited debate around the role of greenhouse gases in Earth’s long-term climate history, claiming that atmospheric carbon dioxide and methane levels remained largely stable during a major cooling period around 2.7 million years ago.

Drawing on findings from Antarctic “blue ice” samples extending climate records beyond 800,000 years, the research suggests CO₂ levels hovered near 250 parts per million with minimal variation, even as global temperatures declined and ice ages intensified.

The interpretation has been met with mixed reactions, with some scientists arguing the results point to greater climate sensitivity to even small gas fluctuations, while critics say the findings highlight the role of natural variability rather than greenhouse gases as primary drivers.

Shock New Evidence Showing No Link Between CO2 and Temperature Over Last Three Million Years Stumps Net Zero Activists | Chris Morrison, Watts Up With That?

The climate science world (‘settled’ division) is in shock following the discovery in ancient ice cores that levels of… pic.twitter.com/EmOyHBm8UY

— Owen Gregorian (@OwenGregorian) March 29, 2026