100,000-year problem

Variations in the amount of incident solar energy drive changes in the climate of the Earth, and are recognised as a key factor in the timing of initiation and termination of glaciations.

While there is a Milankovitch cycle in the range of 100,000 years, related to Earth's orbital eccentricity, its contribution to variation in insolation is much smaller than those of precession and obliquity.

The related 400,000-year problem refers to the absence of a 400,000-year periodicity due to orbital eccentricity in the geological temperature record over the past 1.2 million years.

This fractionation is controlled mainly by the amount of water locked up in ice and the absolute temperature of the planet and has allowed a timescale of marine isotope stages to be constructed.

[4] Elkibbi and Rial (2001) identified the 100 ka cycle as one of five main challenges met by the Milankovitch model of orbital forcing of the ice ages.

[5] As the 100,000-year periodicity only dominates the climate of the past million years, there is insufficient information to separate the component frequencies of eccentricity using spectral analysis, making the reliable detection of significant longer-term trends more difficult, although the spectral analysis of much longer palaeoclimate records, such as the Lisiecki and Raymo stack of marine cores[6] and James Zachos' composite isotopic record, helps to put the last million years in a longer-term context.

[11] The 100,000-year problem has been scrutinized by José A. Rial, Jeseung Oh and Elizabeth Reischmann[12] who find that master-slave synchronization between the climate system's natural frequencies and the eccentricity forcing started the 100 ky ice ages of the late Pleistocene and explain their large amplitude.

While it is possible that the less significant, and originally overlooked, inclination variability has a deep effect on climate,[13] the eccentricity only modifies insolation by a small amount: 1–2% of the shift caused by the 21,000-year precession and 41,000-year obliquity cycles.

[21][22] The recovery of higher-resolution ice cores spanning more of the past 1,000,000 years by the ongoing EPICA project may help shed more light on the matter.

A new, high-precision dating method developed by the team[23] allows better correlation of the various factors involved and puts the ice core chronologies on a stronger temporal footing, endorsing the traditional Milankovitch hypothesis, that climate variations are controlled by insolation in the northern hemisphere.

The establishment of leads and lags against different orbital forcing components with this method—which uses the direct insolation control over nitrogen-oxygen ratios in ice core bubbles—is in principle a great improvement in the temporal resolution of these records and another significant validation of the Milankovitch hypothesis.

δ 18 O , a proxy for temperature, for the last 600,000 years (an average from several deep sea sediment carbonate samples) [ a ]
A δ 18 O record for the past 140,000 years from Greenland ( NGRIP ) and Antarctica ( EPICA , Vostok ) ice cores
Diagram shows that obliquity varies from 22.1 to 24.5 degrees.
The effect of obliquity variations may, in concert with precession, be amplified by orbital inclination.
Drawing shows the preseasonal change in orbital inclination as the earth turns counter-clock wise.
Precessional cycles may produce a 100,000-year effect.
The lighter coloring of irregular patches in the Atlantic Ocean off France shows where algae are blooming.
An algal bloom . The relative importance of land- and sea-based photosynthesis may fluctuate on a 100,000-year timescale.