CO2 Levels Over 6M Years
Based on the search results, here is a summary of CO2 levels for the last 6 million years:
Ordovician period (500 million years ago): CO2 concentrations were extremely high, ranging from 3000 to 9000 ppm.
Phanerozoic eon (541 million years ago to present): CO2 levels fluctuated, with periods of high concentrations and others of lower levels. During the Pliocene era (3 million years ago), CO2 levels were similar to today’s, ranging from 300 to 400 ppm. Temperatures were 2-3°C (3.6-5.4°F) above pre-industrial levels, and sea levels were 15-25 meters higher.
Mid-Pliocene (3 million years ago): CO2 concentrations were around 300-400 ppm, with temperatures 2-3°C (3.6-5.4°F) above pre-industrial levels and sea levels 15-25 meters higher.
Oligocene era (33-23 million years ago): CO2 levels dropped to around 1000 ppm, with temperatures still 4-6°C (7.2-10.8°F) higher than today.
Pre-industrial era (before 1800s): CO2 levels were around 280 ppm.
Industrial era (1800s-present): CO2 levels have increased rapidly, with the global average setting a new record high in 2023 at 419.3 ppm. The annual rate of increase is about 100 times faster than previous natural increases.