A new study has confirmed that the Gulf Stream, a crucial ocean current that helps regulate climate and sea levels, is weakening. The flow of warm water through the Florida Straits has slowed by 4% over the past four decades. This slowdown has significant implications for the world's climate, and scientists are concerned that it may be a sign of further weakening to come.
Maybe I'm a pessimist, but I don't think they ever will.
It's probably not going to be a whole city at once. It's going to be a building here, a building there, barely escalating beyond local news unless it's a famous building (Mar-A-Lago?). There's going to be more and worse hurricanes, but climate deniers will point out how they weren't as bad as Katrina or Maria or Sandy. Insurers have already started leaving those areas, changing policies, and/or hiking rates.
The big exception will be if another New Orleans levy breaks. But people will blame the very idea of that city existing below sea level as being an inherently bad idea (which… I don't think is entirely wrong) and use that to deflect away from the influence of climate change.
People still denying climate change today are either financially invested in doing so, or will need a ridiculous and dramatic event to convince them. Something like you would see in a disaster movie, like a 300ft tall Tsunami.