Researchers Just Sampled 1.4-Billion-Year-Old Air—and It’s Not What They Expected

“around 1.4 billion years ago, during the Mesoproterozoic era (1.6 to 1.0 billion years ago), Earth’s atmosphere contained ten times more carbon dioxide than today. This high CO2 level helped maintain a climate similar to the present, even though the Sun was significantly weaker at the time. These high levels, along with temperature estimates based on the salt, indicate that the Mesoproterozoic climate was more mild than researchers theorized.

The atmosphere also had 3.7% of today’s oxygen levels. While this might not seem like a lot, it’s still an unexpectedly high quantity“

https://gizmodo.com/researchers-just-sampled-1-4-billion-year-old-air-and-its-not-what-they-expected-2000706812