So, there are a few interesting nuances here. First, we've already passed 400 PPM CO2, and it's very hard to imagine we won't hit 500 PPM. It's entirely possib

So, there are a few interesting nuances here. First, we've already passed 400 PPM CO2, and it's very hard to imagine we won't hit 500 PPM. It's entirely possible we'll hit 600 PPM. It's very crucial how much warming is really associated with these various CO2 levels - and that is not known to a high precision at this time. If energy technology is developed as it should be, with solar, nuclear, wind, and geothermal continuously being improved, CO2 emissions will fall off pretty quickly over the next few decades. It seems likely this can be done with constantly increasing quality of life. The real issue is how will we mitigate the peak atmospheric CO2 concentration if needed? I would argue the only sane approach is aggressive investment into science and technology. Mitigations may have to include many things, even up to the scope of orbital sunshades.