Where did all that oil and gas and coal come from in the first place.
Answer: Plants and algae and geological processes sucked it out of the atmosphere and buried it. In the early Earth, the CO2 ppm was 800,000 versus today's 380.
Plants and algae got so good at this process that by 6 to 8 million years ago, they had absorbed out just about as much C02 as possible, down to 500 ppm.
The Earth started to dry out after this period. Jungles and temperate rainforests receded in favor of grasslands, savanna and deserts.
By 3.0 million years ago, regular glaciation cycles started to overtake Europe, Asia, North America and mountaineous regions.
Greenland and Antarctica stayed glaciated just as they had been for 15 million years in the case of Greenland (when it was much warmer and wetter and C02 concentrations were much higher by the way - ie Greenland is not going to melt) and for 35 million years in the case of Antarctica (CO2 ppm was 3000 when Antarctica started freezing over - ie. there is no way Antarctica is going to melt either.)
So in the past, when C02 was higher, what did we have, say 10 million years ago?
Lush Rainforests, rapid plant growth, no deserts, comfortable living for the animal family which dominated the planet at the time, the Apes (our family). At that time, there were over 50 different species of Apes on the planet, the dominate family of animals, while today there are only 4.
It seems to me that we were built for higher CO2 concentrations. We certainly were not built for the 180 ppm of CO2 that resulted in the last 4 ice ages. We are a naked Ape for example.
It is actually quite pleasant in a greenhouse and plants seem to grow really well in them too - the climate scientists are so wrapped up in their own little panic that they cannot see the forest for the ice in the way.
The main problem is the pace at which climate change-related effects could happen over the next couple of centuries. The faster the pace, the harder it would be to adapt to the changes (and a faster pace implies a higher likelihood of abrupt and unanticipated effects).
We certainly were not built for the 180 ppm of CO2 that resulted in the last 4 ice ages. We are a naked Ape for example.
Well, pre-historical humans managed to muddle through the glacial epochs. They may not have enjoyed it.