It is absolutely not our growth as a population that has affected climate change. That's capitalist doomer propaganda. Those actually responsible for it are the few at the top of capitalist hierarchies. Politicians, billionaires, oil and coal barons. Right now we van feed up to 11 billion people, yet there is still mass starvation and poverty. Capitalists require poverty so that people are desperate enough to work the shitty jobs the capitalists "create".
As for the rest of what you said, I briefly touched upon this, but even CCP and USSR admitt(ed) they weren't really communist, and whether they're socialist is extremely debatable. They're not communist because by their own admission they're preparing for a communist world, but they keep saying that and it never comes about. These regimes lie constantly, but even if they lied rarely I'd still not believe they want actual communism because it'd involve giving up their power. What these states actually are is state capitalist.
They're communist in the same way the Nazis were socialist, or the DPRK is a democratic republic: they're not.