The Vostok ice core — drilled from the Antarctic ice sheet between 1980 and 1998 — extends 3,623 meters into the ice and contains a climate record spanning 420,000 years. The EPICA Dome C core, completed in 2004, extends this record to 800,000 years. These cores contain trapped air bubbles — actual samples of ancient atmosphere, preserved at depth by the accumulating weight of snow above them — that allow scientists to measure the precise composition of the atmosphere at the time each layer was deposited. The data they contain is not a proxy, not an inference, not a model output. It is a direct measurement of ancient air. The air from 800,000 years ago is in those bubbles. You can analyze it. The analysis is reproducible. It has been reproduced by multiple independent research groups using multiple independent methodologies. The results are always the same. The result that matters most: In 800,000 years of atmospheric record, CO2 concentrations never exceeded 300 parts per million. The natural cycle of ice ages and warm periods produced CO2 fluctuations between approximately 180 parts per million during glacial maxima and 280 parts per million during warm interglacial periods. This range — 180 to 280 — is the range within which the climate system that produced every ecosystem on Earth, every species currently alive, and every human civilization ever built operated. The current atmospheric CO2 concentration is 421 parts per million. It crossed 300 for the first time in human history in approximately 1912. It crossed 400 for the first time in approximately 3 million years in 2013. The rate of increase — approximately 2.5 parts per million per year currently — is 100 times faster than any natural rate of change in the 800,000 year record. We have taken the atmosphere outside the range it has occupied for 800,000 years and we are moving it further outside that range faster than anything in the geological record. The significance of this cannot be overstated. Every biological adaptation — every physiological process, every ecological relationship, every seasonal cycle of every species on Earth — evolved within that 180 to 280 range. The timing of flowering, the navigation of migratory species, the coral bleaching threshold, the snowpack that feeds rivers — all of it calibrated to a climate system operating within a range that no longer exists.