Your belief that everything could just be solved with renewables is incredibly naive. It's simply not proven that it can be done yet. And even renewables produce a lot of CO2. Even if they produce less than fossile fuels, the needs for 11 Billion people would be significant.
A richer lifestyle means more CO2.
I don't even know where you get your beliefs from, that CO2 neutral life would be easy and cheap.
As for counteracting phenomena: again, it is not a law of nature that birth rates drop as people get wealthier. Even now for example there are subgroups in wealthy nations that still have high birth rates. I'm not saying it WILL happen, just that it can. And 50 years are not a very long timespan to observe to be assured about the effect of dropping birth rates.
A richer lifestyle means more CO2.
I don't even know where you get your beliefs from, that CO2 neutral life would be easy and cheap.
As for counteracting phenomena: again, it is not a law of nature that birth rates drop as people get wealthier. Even now for example there are subgroups in wealthy nations that still have high birth rates. I'm not saying it WILL happen, just that it can. And 50 years are not a very long timespan to observe to be assured about the effect of dropping birth rates.