The Core

We're going to die.

The Core

The Earth was built to last. It is a 4,550,000,000-year-old, 5,973,600,000,000,000,000,000-tonne ball of iron. It has taken more devastating asteroid hits in its lifetime than you've had hot dinners, and lo, it still orbits merrily. But now it's going to freeze over

The Earth Goes Cold

Once the core has solidifed it can no longer generate a magnetic field. There may be some frozen in field, but I would guess that the strength of the magnetic field with decrease as more and more of the core freezes, so any residual field is likely to be small. The core of Mars is thought to be frozen and it's magnetic field is negligable.

Anyhow, the main problem would be that without the magnetosphere to protect it the atmosphere will gradually be stripped by the solar wind and we'll be left with nothing to breathe. In addition, without an atmosphere the surface will be subject to wide temperature swings; just as the Moon is in fact.