Abstract
A parameterized fit to 5.3 million years of Benthic foram dO18 data is described, which quantifies the magnitude, phase, and variability of Milankowitz terms. The 41,000y obliquity cycle, and 100,000y ellipticity cycles are dominant, with interglacial periods correlated with large orbital ellipticity. Shorter regular warming peaks correlate with larger obliquity. The fit is then used to extrapolate forward in time implying that the earth will begin cooling in about 2000 years time, eventually entering another 70,000 year long glaciation. Possible causes resulting from effects in the tropics due to increased eccentricity, and to changes in albedo at large obliquity, are discussed.
Highlights
The exact cause and evolution of ice ages still remain a mystery (Raymo & Huybers, 2008)
The correlation between summer insolation at 60°N and glacial periods is not really that convincing (Houghton, 1994), and geological evidence shows that temperature changes were global with 2-3 degree changes occurring in the tropics (Hostetler & Mix, 1999)
A fit to 5.3 million years of Benthic foram dO18 data quantifies the relative importance of different Milankowitz cycles
Summary
The exact cause and evolution of ice ages still remain a mystery (Raymo & Huybers, 2008). The favoured hypothesis of how ice ages develop is that orbital changes which induce cooler summers in the Northern Hemisphere lead to less summer melting of winter ice allowing a spread of glacial coverage This effect is enhanced further through feedback from increased ice albedo, and falling levels of atmospheric CO2 and water vapor. The work presented in this paper does not attempt to explain the origin of the ice ages, but instead tries to parameterize the observed temperature dependencies and thereby derive quantitative information. This approach applied in other branches of physics is usually called phenomenology (Note 1)
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