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!
In the year 535 AD volcanos in Iceland spewed sun blocking gases and particles into the upper atmosphere. This caused 2 years of dark and nobody saw the sun for this entire period. Crops failed and there was no summers. A large percentage of the human race died from cold, starvation and disease.
Intentionally spraying stuff into the atmosphere to dim the sun should be considered a crime against humanity.
Nuclear winter, anyone?
From articles from NASA recently,there have been NO solar activity for about a year,so it seems the Sun is taking care of itself.
The prediction from NASA scientists therefore is we will be in for a colder than normal time period in the coming months.
I bet you have seen none of this from the usual subjects