Orphan 55

Orphan 55 was the name given to Earth in one possible timeline, where it was designated as an orphan planet after nuclear war and global catastrophes rendered it a barren wasteland. After seeing the planet's history, the Thirteenth Doctor stated that it started with global warming and then "the food chain collapses. Mass migration. And war." In order to survive the radiation and carbon dioxide atmosphere, what remained of humanity evolved into mutants known as Dregs. The planet also appeared to have holes in the ozone as Kane stated that direct solar radiation when the sun came out for more than ten minutes would be fatal.

Eventually, Kane built the Tranquility Spa on the planet in what used to be Siberia, taking advantage of the open space. The spa was only made accessible via teleport, and concealed the outside world from visitors. Kane eventually intended to terraform the planet to be livable again using the proceeds from the spa. The Thirteenth Doctor and Team TARDIS arrived soon before the spa was attacked by Dregs, and uncovered the true nature of Kane's resort and the planet beyond. After escaping, the Doctor told her companions that Orphan 55 was just one possible future for the Earth and that it wasn't set in stone that the Earth would end up as an orphan planet. If humanity made the right choices, the timeline in which Orphan 55 existed could be averted. (TV: Orphan 55)

Behind the scenes

 * The Earth appearing as Orphan 55 is a unique deviation from the future history established for Earth in the Doctor Who universe, particularly as Orphan 55 is identified as not being from an alternate timeline but a possible future that could still happen. In other instances where ruined versions of Earth have appeared, it has always been established as being in an alternate timeline that is usually averted by the Doctor and/or their companions.