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Early Pleistocene Glacial Cycles and the Integrated Summer Insolation Forcing

Fig. 3B. Seasonal variations in insolation at 65N
Seasonal variations in insolation at 65°N when perihelion occurs at Northern Hemisphere summer solstice (red), fall equinox (orange), winter solstice (blue), and spring equinox (light blue).

Early Pleistocene Glacial Cycles and the Integrated Summer Insolation Forcing.
Science
Vol. 313, Issue 5786, pp. 508-511, 10.1126/science.1125249, 28 July 2006.

Peter Huybers
Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA.
ABSTRACT:
Long-term variations in Northern Hemisphere summer insolation are generally thought to control glaciation. But the intensity of summer insolation is primarily controlled by 20,000-year cycles in the precession of the equinoxes, whereas early Pleistocene glacial cycles occur at 40,000-year intervals, matching the period of changes in Earth's obliquity. The resolution of this 40,000-year problem is that glaciers are sensitive to insolation integrated over the duration of the summer. The integrated summer insolation is primarily controlled by obliquity and not precession because, by Kepler's second law, the duration of the summer is inversely proportional to Earth's distance from the Sun.
Download data from the WDC Paleo archive:
Data Description

Matlab program code used to generate the insolation values:
daily_insolation.m, orbital_parameter_data.mat, and make_integrated_insolation_tables.m

Integrated summer insolation values (800K data files) for:
90° North , 85° North, 80° North, 75° North, 70° North, 65° North, 60° North, 55° North, 50° North, 45° North, 40° North, 35° North, 30° North, 25° North, 20° North, 15° North, 10° North, 5° North, 0°, 5° South 10° South, 15° South, 20° South, 25° South, 30° South, 35° South, 40° South, 45° South, 50° South, 55° South, 60° South, 65° South, 70° South, 75° South, 80° South, 85° South, 90° South.

To read or view the full study, please visit the Science website.
It was published in Science, Vol. 313, Issue 5786, pp. 508-511, 10.1126/science.1125249, 28 July 2006.
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