Timeline (Orphan 55)

In one timeline, Earth became an orphan planet designated Orphan 55 caused by global catastrophes started by global warming and nuclear war. As the Thirteenth Doctor explained to her companions, who came from the year 2020, this timeline was but "one possible future" and it could still be averted if humanity made the right choices. However, the Doctor couldn't promise that it wouldn't end up being the Earth's future. (TV: Orphan 55)