Winter Is Coming: I Will Build a Peach Blossom Garden in the Last Days

[Real counter-routine + apocalypse + hoarding supplies + decisive killing + blackening of the Holy Mother + non-rebirth + non-system + no space ability + consistent with science] Solar radiation has dropped dramatically, an unusually cold winter has arrived, and the world has been covered in ice and snow. The temperature in the Golden Sea has dropped to minus 50 degrees Celsius, while the North Pole and Antarctica are close to absolute zero. How can a protagonist without space powers survive in the apocalypse with only a master key?