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100,000-year problem is a discrepancy between the climate response (as measured by proxies for the temperature and extent of glaciations) and the forcing from the amount of incoming solar radiation, or insolation, which has little power on a 100,000 year (100 ka) timescale.

Due to variations in the Earth's orbit, the amount of insolation varies with periods of around 21,000, 40,000, 100,000, and 400,000 years. Variations in the amount of solar heating drive changes in the climate of the Earth, and are recognised as a key factor in the timing of initiation and termination of ice ages. Spectral analysis shows that the most powerful climate response is at 100,000‑year period, but the orbital forcing at this period is small.