I get that, but I think you might also be missing something in the urgency to derive one particular meaning from the metaphor.
Imagine coming upon a window that was broken, and inferring that it must have been broken by "a thing". So you look for evidence - a rock, a hammer, something - all the while proclaiming that the cause was a given. All the while, you overlook that the initial fracture was there from the beginning and carried along every day by comparatively small amounts of thermal stress.
Could that also be a metaphor for some of the climate change hype? (I don't use the word "hype" to imply false. I use it in the context of "to promote or publicize extravagantly".)
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.
> Isn't this more akin to saying, the window broke before the hammer hit it, so the hammer couldn't have been the cause?
Agree or disagree, it's an interesting thought exercise that took the original analogy in an interesting direction. Whether or not you agree about it being interesting or useful, it certainly wasn't "arguing the metaphor", just adding to it in a way that you may or may not appreciate.
That's what arguing the metaphor is. It's adding to it to change or subvert the meaning and change the direction of the conversation.
We don't appreciate it when politicians twist questions to give the canned responses they've prepared, why should we accept a similar tactic amongst ourselves?
> Scientists generally regard the later part of the 19th century as the point at which human activity started influencing the climate. But the new study brings that date forward to the 1830s.
He's saying it's hard to predict results from certain causes because the process is chaotic.