According to Hokkaido University, the consortium, which is made up of more than 16 researchers from 80 countries around the world, analyzed and evaluated the record of geological samples collected and published in Antarctica to date, and based on current knowledge. Atmospheric CO2 concentration has been updated.

　The results showed that from 6,600 million years ago to 5,600 million years ago, the earliest period of the Cenozoic Era, the atmospheric CO2 concentration was 420 to 600 ppm, much higher than the current 700 ppm. The highest temperature reached 5,000 ppm 1,600 million years ago, when temperatures were estimated to be 12 degrees warmer than today.

　After that, the atmospheric CO2 concentration gradually decreased and the Antarctic ice sheet began to form by 3,400 million years ago, but the CO2 concentration remained higher than today until 1,600 ppm, 480 million years ago. The temperature at that time is thought to have been 4 to 5 degrees warmer than it is now.

　It reached its current level 1,400 million years ago, and fell to 250 PPM 280 million years ago, ushering in an ice age when continental glaciers developed in the Northern Hemisphere. It is estimated that when humans first appeared 40 years ago, it was at that level or even lower.

　The main cause of the ongoing global warming is thought to be the rise in atmospheric CO2 concentration due to fossil fuel consumption, which has continued since the Industrial Revolution. The consortium believes that by continuing this research, more reliable knowledge about the relationship between atmospheric CO2 concentration and temperature will be obtained.

Paper information:[Science] Towards a Cenozoic History of Atmospheric CO2