Peter,
I don’t think it is disingenuous at all to talk about increasing greenhouse gases changing the overall probabilistic environment of any single weather event. And the increase in atmospheric and ocean temperatures are just one of the effects of increasing CO2 on the overall environment. It is one metric to meaure the effects on “weather”, but certainly there can be others…i.e. stronger and more frequent severe weather events.
The marble and metal sheet mind experiment is only to illustrate how probabilities must be considered in a wholistic way, and thus, when global climate models show a likely increase in extreme weather events, then it should be considered as well in a wholistic way as part of a new probabilistic environment Any single weather event exists as part of that environment, and thus, you can’t dissect it out. It has multiple causes, all interacting, all part of the whole, and some of those causes as part of that whole must, by fact, include increasing anthropogenic greenhouse gas concentrations.