Point out where I said or even hinted that it's China's turn to go full throttle colonialist power. China might be putting some nails in some coffins and putting dirt on others, but those coffins were already in the ground from past colonialism. That is not an excuse, but the reality of the situation...it's historical fact. It's a fact that white european colonialists(and later US ones) are the driving force for the current poverty, pollution, violence, and extinct animals today. It's also pretty worthless to go after the Turks, Greeks, Italians, Moroccans, Huns, Egyptians, Persians, or whichever previous nation-state that is no longer a world power when they have practically nothing they can contribute compared to the US and wealthy european countries.
The problem stems from people expecting them to be better than the Western colonialists and clean up the mess that the West left.
Here is where you explicitly said that it's OK for China to be colonialist as we shouldn't "expect better" of them; it implies that, like a child's toy that must be shared around, China should not be criticised for having "their turn" at the colonialist's game. You do so again in the very next sentence by deflecting blame from China's involvement in the extinction of today's species because "the West did more harm!" Yes, they did, but this thread isn't about who did more harm, it's about a specific issue that "the West" has little to do with; if people want to criticise China for it then they should be allowed to do so as, frankly, there is no excuse for what they're doing.
I don't see how it's "worthless" to look at those other countries in the context of deflecting colonialist blame. You argued that China should have no expectations of "being better", and therefore should hold no blame for their actions, due to the colonialist sins of the past. This logic could be applied to those same colonialist sins; why should, for example, Britain have been "expected" to be any better than any other empire that had come before them? The British Empire was created due in part to the country wanting to emulate the continued prominence and wealth enjoyed by the Portugese and Spanish Empires at the time; what difference is there to China wanting to emulate the continued prominence and wealth of the 'American Empire' today? Also, since we're dealing so heavily in whataboutism here what about the USSR/Russia? Why is Russia suddenly exempt "the tab" despite them being one of, if not the most destructive colonialist forces of the 20th century? One that also had similar levels of influence over China in the 20th century as Britain had during the century prior. It can't be because they are currently not as powerful because 1) neither is Britain and 2) they are still very, very powerful.
The thing is, when you start throwing around whataboutisms, you have to be expected to apply that logic fairly. You can't argue one thing for one country and another thing for another; that is unless you have a vested interest in deflecting blame.
Europe and the US have inherited the spoils of prior colonialism, so what's with the cognitive dissonance with them needing to pay reparations and how it ties into where China's responsibility starts? Despite China becoming a heavier hitter, it's still not the US and China is going to be held responsible for it's own shit show. IF China inherits the spoils of previous colonialism to become the new sole superpower, then we can talk about how they can pick up the tab.
What do you mean cognitive dissonance? I was saying that Western reparations for its own colonialism have nothing to do with what China is doing now, and that's true. The sins of the past do not override the sins of the present, you can't use one to deflect blame from another, because if that was a viable strategy then literally no progress could ever be made on anything.
As for the rest; are you honestly arguing that China has no role to play in fixing current environmental issues because they aren't the "sole superpower"? China is a country of over a billion people and it's political sway is rivalled pretty much exclusively by the United States; it should be expected to pick up the tab because, despite your insistence, global climate change is exactly that, global. Talking about global climate change as a if it were a "tab" that needs to be "picked up" instead of a global crisis that will affect literally everyone will get us no where.
Yes, it may not be perfectly "fair" that China has to put in some effort to curb a crisis that was kick-started by forces other than themselves. You know what isn't fair? Dying due to toxic air, being forced to leave your home (or being born without one) due to the encroachment of the sea and the heat, starving due to the failure of crops, and only being able to see animals such as the Rhino and Tiger in history books from before you were born. Climate change isn't something we should be playing games of "who to blame!" over, it's something that we must, globally, do everything we can to solve. Refusing to condemn a nation due to some preconceived notion of "fairness" will do absolutely nothing to help solve it.