There is no such thing as an ideal CO2 level. Life in general, and humans in particular, can exist in a world of far more or far less CO2. The problem is our m

There is no such thing as an ideal CO2 level. Life in general, and humans in particular, can exist in a world of far more or far less CO2. The problem is our modern, industrial civilization is built on the assumptions that future world is very much like the current world. Everything from houses to cities to nations are built around these long-term assumptions. The danger of climate change is that we erode the very foundations we've built our civilization on. The danger is not some arbitrary level, it is the rapid change to that level.