That's an entirely different metaphor though.

That's the point.

He's not talking about the causes of climate change or anything like that. He's explaining a specific phenomenon using an analogy. Whether or not you believe climate change is anthropocentric is immaterial to how this phenomenon manifests. And to help people understand how this phenomenon works, he used the metaphor of the shattered glass.

It actually does not matter what shattered the glass. He said hammer because a hammer would work. It could have been smashed with a frozen, medium-sized cat for all it mattered.

The point is, once the glass is shattered, you cannot predict where each piece is going to fall.