20,000 years ago, during the last Glacial Maximum, CO2 actually dropped to 180 parts per million, or 0.018%.
That was the lowest verifiable reading in Earth's history.
At 150 ppm (0.015%), it is likely that every large land animal - including humans - would have died because all the edible plants would have died.
Oh, and before we seriously start talking about dimming the sun, it might be a good idea to remember that we have been in an Ice Age for the last 3.2 million years.
We are currently in an “Interglacial” warm period, which typically lasts 10,000 to 25,000 years.
I'm not sure how they measure the start of a warm period, but our current Interglacial started at least 15,000 years ago.
20,000 years ago, every major USA city from Seattle to Chicago to New York City was under at least a thousand feet of ice!
Wow I didn’t know that. I read if it hit 0.02% plants start dying but I guess it’s 0.015%. How did it get so low? I would think with everything covered in ice the CO2 wouldn’t be absorbed by plant life etc. Proves the earth can lower it on its own though, but these people are insane, talking about blocking out the sun. Like hell they will. I’m 56 and lived in New York all my life on Long Island by the ocean. I remember clear as day the temperature and climate from when I was 2 years old and NOTHING nothing has changed here. It’s the same every year, no odd feelings about the seasons, temp, climate, every summer the temps hit the 90s and every winter we hit down as low at 10 degrees. Actually in 2016 we hit as low as zero in January. But my point being is if we had any substantial change in climate, I certainly would have noticed it from living in the same place for 56 years, the temps are the same and the sea water isn’t rising up. Matter of fact by Long Island sound there’s this pier that has been in place since the 1800s. It’s STILL above the water line. Why, if the polar caps are melting? But I guess now liberals will tell us “Oh, climate change only happens in certain sections of the earth” yeah sure, the atmosphere stays completely static.