“…The last time the planet had a concentration of 300 to 400 ppm of CO2 in the atmosphere was during the mid-Pliocene, 3 million years ago — recently enough for the planet to be not radically different than it is today. Back then, temperatures were 2 degrees C to 3 degrees C (3.6 to 5.4°F) above pre-industrial temperatures (though more than 10 degrees C hotter in the Arctic), and sea levels were at least 15-25 meters higher. Forest grew in the Canadian north and grasslands abounded worldwide; the Sahara was probably covered in vegetation. Homo habilis (aka “handy man”), the first species in the Homo line and probably the first stone-tool users, got a taste of this climate as they arrived on the scene 2.8 million years ago. (Homo sapiens didn’t show up until 400,000 years ago at the earliest.)…” This according to an excerpt from Yale E360.
Headline image: Arnold Paul