Life on Earth was nearly doomed by too little CO2 | Watts Up With That?:
"During the last ice age, too little atmospheric carbon dioxide almost eradicated mankind
...Statistician Bjorn Lomborg had already pointed out that the Paris CO2 emission promises would cost $100 trillion dollars that no one has, and make only a 0.05 degree difference in Earth’s 2100 AD temperature.
...What few realize, however, is that during the last Ice Age too little CO2 in the air almost eradicated mankind.
That’s when much-colder water in oceans (that were 400 feet shallower than today) sucked most of the carbon dioxide from the air; half of North America, Europe and Asia were buried under mile-high glaciers that obliterated everything in their paths; and bitterly cold temperatures further retarded plant growth.
In fact, Earth’s atmosphere had only about 180 parts per million CO2, compared to today’s 400 ppm: 0.018% then versus 0.040% today.
...When that Ice Age ended, moreover, CO2 changes didn’t lead the warming. The atmospheric CO2 only began to recover about 800 years after the warming started.
Carbon dioxide truly is “the gas of life...”