What is 100,000-year problem?
[[File:Delta-O-18 in deep sea sediment-svg.svg|thumb|alt=link, a proxy for temperature, for the last 600,000 years (an average from several deep sea sediment carbonate samples) |link, a proxy for temperature, for the last 600,000 years (an average from several deep sea sediment carbonate samples)]] The amount of incoming solar radiation, also called [[insolation]] determines the temperature on Earth. This temperature rises and falls according to the strength of radiation given off by the [[sun]], the distance from the earth to the sun, and the tilt of the Earth's axis of rotation. However, the recent change between glacial and inter-glacial states that occurs on a circa 100,000 year ('''100 ka''') timescale, does not correlate well with these factors. This is known as the '''100,000 year problem'''. Due to [[milankovich cycle|variations in the Earth's orbit]], the amount of insolation varies; there are periods of around 21,000, 40,000, 100,000, and 400,000 years. Variations in the amount of solar energy drive changes in the [[climate]] of the Earth, and are recognised as a key factor in the timing of start and termination of [[glaciation]]s. Looking at [[strata]], [[isotope analysis]] can be performed. One of the most precise methods consist in using [[Oxygen-18]]. The amount of oxygen 18 mainly depends on the amount of ice that can be found and on the temperature of the planet. There are different [[hypothesis|hypotheses]] to explain the [[phenomenon]]: * There may be an internal frequency to the climatic system found on earth. This [[resonance]] may be 100,000 years. * The Orbital inclination has a frequency of 100,000 years. * The planets rotate around the sun in an [[ellipse|elliptical]] orbit. These orbits change over time. For the earth, this change has a frequency of 21,636 years. In an [[ice age]], the buildup of ice is slow, but the melting of the ice is fast. * The luminosity of the sun may change over time. This would influence the phenomenon * The amount of [[photosynthesis]] on water-dwelling orga