Relying on an economic system to make moral decisions is like driving in screws with a hammer.

Capitalism is not perfect, but at least to me this is more of a moral issue than an economic one.

I think your CO2 point is a great example, why would a Communist or Socialist economic system be inherently more eco-friendly than a Capitalist system? You now have a system where there is a government willing to "plan" or "intervene" in certain aspects of the economy, but unless the government actually cares about pollution nothing will happen. You could even theoretically have a centrally-planned economy that WANTS to increase emissions.

The largest polluter in the world is a Communist country, and in the last 30 years their CO2 emissions have sextupled, while the US's emissions per year have remained flat.

Morality != Economics