Humans have caused 1.5 °C of long-term global warming according to new estimates

Asking sincerely because I'm not well-versed on this topic - do we have actual proof that humans are causing global warming?

My understanding is that the climate will change independently of human activity. For example, we know that there was an Ice Age and it was not ended by human activity but rather natural processes. So the climate has been known to change historically without human involvement.

So here is where I'm looking for clarification: I thought the "controversy" over climate change was the degree to which human activity is accelerating a natural process of warming?

Said differently, the planet is warming by itself, but humans pumping hydrocarbons and other things into the atmosphere is speeding up that process. But the cause is not solely because of human activity.

Thanks in advance for thoughtful responses, I'm really just trying to learn here.