Let's pretend, just for the sake of conversation, that the polar ice caps completely melt sometime in the next century for some reason. Let's just pretend. I don't care why. What happens to Major League Baseball?
To answer that I found a map of what the earth will look like when the oceans rise and combined it with a map of current MLB stadiums. Look:
Mercator projection on top of a globe, so some differences are unavoidable. Map credits: National Geographic | Reddit Baseball
Count 'em up: We'd lose both clubs in New York, the Red Sox, the Phillies, the Orioles, the Nationals, the entire state of Florida (not that anybody goes to games there anyway), the Astros, probably both the Giants and Athletics, and the Mariners. Twelve of thirty MLB stadiums, or forty percent of baseball. GONE.
Hope you didn't need to sleep tonight.