Most people are wrong here. It IS actually possible to communicate between two airgapped computers with temperature changes, but the data transfer rate is too slow (1-8b/hr) to be effective.
The underlying point Noam makes is true though: there are a deluge of crazy airgapped comms techniques like EM emanations from DRAM clocks that get a lot faster (300kbps).
This isn’t sci-fi. We vastly underestimate what AI can do with perfect knowledge of all of this literature.