travel between underground cities 100 years from now:

 Will be primarily accomplished by tunnels underground. Though there might be above ground roads they would have to withstand 300 to 500 mph winds periodically and so would have to be especially designed. Flying in planes could also happen sometimes during the year most places. Boats might become more like submarines so they can go deep enough to get away from the winds and waves on the surface of the oceans. So, in high winds in shallow water this isn't going to work. So, any way you look at it travel of any kind is kind of dicey sometimes or impossible other times unless you are traveling underground or by submarine in deeper waters. So, likely tunnels would be built below ground and then in shallower waters the tunnels would continue out into the shallower parts of seas for cargo submarines between different points on earth during the many storms of one kind or another that would exist then. So, the kind of technology one might see in space would be adapted to sea going travel with air locks keeping out water while moving cargo under the sea.

The good news to some degree is all these changes are gradual to some degree so at least some of the people will have time to adapt to them. It's sort of like how many people died of Covid-19. If you could adapt fast enough to the changes you survived. If you couldn't adapt fast enough to the changes you died or got long covid. The same will be true of the whole next 100 years and beyond here on earth.