When was the last time in Earth history that CO2 was around 400 ppm?

around four million years ago
The last time global carbon dioxide levels were consistently at or above 400 parts per million (ppm) was around four million years ago during a geological period known as the Pliocene Era (between 5.3 million and 2.6 million years ago). The world was about 3℃ warmer and sea levels were higher than today.

When was CO2 380 ppm?

around 3.6 million years ago
The atmospheric burden of CO2 is now comparable to where it was during the Mid-Pliocene Warm Period around 3.6 million years ago, when concentrations of CO2 in the atmosphere ranged from about 380 to 450 parts per million.

When was the last time CO2 was as high as today?

But in at least one respect it was rather similar. This is the last time that carbon dioxide (CO2) levels were as high as they are today. On May 9, 2013, CO2 levels in the air reached the level of 400 parts per million (ppm). This is the first time in human history that this milestone has been passed.

When was atmospheric CO2 last this high?

3 million years ago
In fact, the last time the atmospheric CO₂ amounts were this high was more than 3 million years ago, during the Mid-Pliocene Warm Period, when temperature was 2°–3°C (3.6°–5.4°F) higher than during the pre-industrial era, and sea level was 15–25 meters (50–80 feet) higher than today.

When was the last time we had this much CO2 in the atmosphere?

around 3 million years ago
The last time carbon dioxide was so plentiful in our planet’s atmosphere was in the Pliocene era, around 3 million years ago.

When was CO2 discovered?

Joseph Black, a Scottish chemist and physician, first identified carbon dioxide in the 1750s. At room temperatures (20-25 oC), carbon dioxide is an odourless, colourless gas, which is faintly acidic and non-flammable.

What were CO2 levels 800000 years ago?

Measurements of air in ice cores show that for the past 800,000 years up until the 20th century, the atmospheric CO2 concentration stayed within the range 170 to 300 parts per million (ppm), making the recent rapid rise to more than 400 ppm over 200 years particularly remarkable [figure 3].