Quantity is a quality.

Humans burned stuff for a very long time now, it's when we started burning coal in mass industrially that the global environmental impacts started stacking up to the point of considerable damage.

Ahem. Let's please don't go off into areas outside of the topic and end up repeating political talking points from people with agendas.

Coal, even a home coal fired boiler of the 1940s vintage, is just about as clean as solar, when compared to open cooking fires burning dung, which is the "most popular" method of harnessing combustion on Earth, measured per ton over per capita. Even going from wood to coal is a huge step up in pollution reduction compared to old school methods of burning randomly sourced trees. (Your rocket heater doesn't count. That wasn't even a twinkle in an inventor's eye when coal started to become popular.)

Source: did my senior P-chem work on smog. Then saw the theory made manifest (in a way that no amount of schoolwork could possibly replace) by looking at particulate build-up on a glacier with my own eyeballs. Pollution you can see, and hold in your hand will make this more clear than any amount of chart and graph reading about PM2.5 this and that.

Also: I hate that I had to self-censor my use of emdashes because I don't want my lived experiences to get flagged as chatbot slop. Grrr.