Well, a new study published in the Proceedings of the National Academy of Sciences of the United States of America predicts that our choices are either completely underwater or with some area left high and (relatively) dry. Which means even under the best-case scenario, Miami will stop looking like mainland Florida and start looking more like a string of Islands that are essentially the new northern end of the Florida Keys. (Read an interview with the study's author here.)
The study looked at our future if we continue to release carbon emissions into the atmosphere on the same rate we are now, which would almost certainly lead to the collapse of the West Antarctic ice sheet. The other scenario was that pretty much every country on Earth decided to enact extreme carbon emissions cuts.
The study was accompanied by a mapping tool that lets people compare the various scenarios.
Here's Miami if we leave carbon unchecked until 2100 compared to Miami if we make extreme cuts.
The blue is land that would be underwater completely. You'll notice that's about all that remains in the map on the left. The gray is land that is still above water (though it would likely be prone to flooding... as much of Miami already is now). With extreme carbon cuts, there's still a little something to work with. Miami would live on in some form as basically an archipelago.
Still, wide swaths of the country are underwater. Miami Gardens would be one of the handfuls of U.S. cities with populations over 100,000 that would be completely erased by water.
Now here's Miami if we let unchecked pollution continue until 2050, and if we start making and enforcing carbon cuts until then:
There's still something left of Miami if we leave things unchecked until 2050, but not a whole lot.
And here you can play with the map yourself:
Now one thing these maps don't explain is when Miami would be completely underwater.
"The answer could be sooner than 200 years from now, or as long as 2,000 years," explains the mapping site. "Why the wide range? It is easier to estimate how much ice will eventually melt from a certain amount of warming than how quickly it will melt, which involves more unknowns. The same simple contrast would apply to an ice sculpture in a warm room."
So essentially they're saying that if temperatures continue to rise due to carbon emissions, this is how much we should expect sea levels to rise. We just don't know exactly how long it would take.
Another thing we don't know how long will actually take: getting most of the major industrialized countries across the globe to agree to strict carbon cuts.