The left wing Think Progress reports that about 3 million years ago the CO2 level equalled what we had today. Pray tell, how did that happed? Why wasn't all life made extinct? Humans didn't exist. Was it dinosaur farts that raised the levels so high. Was there another species that reached the level of our civilization? Only to have successive glaciers from five ice ages grind any sign of them to dust? Pardon if I remain a skeptic.
"The last time carbon dioxide levels in the atmosphere were as high as they are today, sea levels were 60 feet higher and it was so warm that trees grew in Antarctica.
Current CO2 levels of 410 parts per million (ppm) were last seen on Earth three million years ago, according to the most detailed reconstruction of the Earth’s climate by researchers at the Potsdam Institute for Climate Impact Research (PIK) and published in Science Advances.
Their in-depth analysis of plant fossils and sediments reveal that such CO2 levels were last seen in the late Pliocene Epoch, a time when there were no ice sheets covering either Greenland or West Antarctica, and much of the East Antarctic ice sheet was gone. Temperatures were up to 7 degrees Fahrenheit warmer globally, at least double that at the poles, and sea levels were some 20 meters (65 feet) higher."
https://thinkprogress.org/carb...p;utm_source=twitter