A study of the Late Paleozoic Ice Age, published in PNAS, found that global temperatures rose about 45.5 degrees Fahrenheit over 175,000 years while atmospheric CO2 doubled from roughly 300 to 700 ppm. Volcanic activity and orbital shifts started the warming, but the second and larger temperature spike came from carbon released by thawing permafrost. That makes the event a clear example of a natural climate feedback loop. Modern Arctic permafrost holds large amounts of organic carbon, and thawing ground is already releasing CO2 and methane. The study does not claim the same timeline will repeat today, since current warming is happening over a century, not millennia. But it does show that once frozen soil starts emitting, it can push temperatures higher and tighten the remaining carbon budget. Researchers still need better data on thaw rates, soil moisture, and methane output before they can make precise projections.
