Yes, CO2 was into the single-digit parts per thousand for much of the dinosaur era. I have no idea how that affected plant growth, but even if that's the cause, it seems tenuous to look at Mesozoic plant growth and assume modern agricultural crops will imitate them. Certainly far more tenuous than the evidence that climate change is causing damage and will cause more.
So you think that rising temperatures may be good for agriculture?
From a website:
As climate change leads to more frequent and intense natural hazards, it is expected that climate displacement will only increase in Bangladesh. The best estimates suggest that up to 18 million people may be displaced by sea level rise alone. http://displacementsolutions.org/ds-initiatives/climate-chan...
Europe us really struggling to deal with the migrants and refugees from Syria. I do wonder how we'll cope with future migrations. It really brings into perspective the idea of a border. Of a country. Just a man drew a line on a map.
It is not tenuous to suggest that modern agricultural crops will yield more in a higher CO2 environment (look into greenhouses). It is actually far less tenuous than speculating that CO2 is causing runaway global warming.