In 1998, a Russian-French-American team pulled a 3,623-meter core from beneath Station Vostok in East Antarctica. The lowest meter contained ice that fell as snow 420,000 years before Homo sapiens walked the planet. For the first time, we had a continuous atmospheric record spanning four glacial cycles — and a CO₂ ceiling of 300 parts per million that the planet had not breached in nearly a million years. We crossed that line in 1912.
The coupling is tighter than we thought
Every ice core tells the same story in deuterium and trapped gas: when CO₂ rises, temperature follows — not as a loose correlation but as a near-mechanical coupling visible across all eight glacial cycles in the EPICA Dome C record. The lag, once thought to be centuries, now looks closer to decades when you account for the time it takes firn to seal into impermeable ice at each drill site.
In 2025, atmospheric CO₂ reached 427 ppm. The Vostok ceiling was 300.
What the ice cannot tell us is what happens when you spike the system by 40 percent in a century rather than over ten thousand years of orbital forcing. The cores describe a world where change was paced by Milankovitch cycles — slow, periodic, bounded. Our experiment has no analog in the ice. That is not a reason to dismiss the data. It is a reason to read it more carefully than ever.