05-23-2012, 03:47 PM

The Azimuth Project

Selected Excerpt:

History

A brief history of Milankovitch cycles and their effect on glaciation is given in:

Michel Crucifix, Glacial-interglacial cycles, in Springer Encyclopaedia of Snow, Ice and Glaciers.

Let us quote a bit:

Joseph Adhémar (1842) formulated the conjecture that the precession of Earth’s orbit caused ice ages, because of its effects on the seasonal distribution of incoming solar radiation (insolation). He realised that one season had to be critical given that the changes in winter and summer insolation caused by precession cancel each other (Herschell, 1830). James Croll (1875) further developed the theory and appreciated the importance of the three Earth orbital elements determining insolation: eccentricity, obliquity (angle between the equator and the ecliptic) and the longitude of the perihelion.

Milutin Milankovitch (1920, 1941) is quoted as the first one to have established a self-contained mathematical theory linking orbital elements to insolation, and insolation to climate changes. On a suggestion of V. Köppen, he calculated the secular evolution of the summer radiation of the northern latitude (published in Köppen and Wegener, 1925), following the hypothesis that glacial cycles are driven by the effects of changes in summer insolation on snow ablation rate during this season (the conjecture had in fact been earlier expressed by Murphy, 1876, and it contradicted Croll’s views). Summer insolation is largest when obliquity is large and/or when summer in the northern hemisphere corresponds to the time of perihelion passing. Milankovitch later substantiated the hypothesis by explicitly calculating the effects of radiation changes on the position of the snow line.

LINK

Selected Excerpt:

History

A brief history of Milankovitch cycles and their effect on glaciation is given in:

Michel Crucifix, Glacial-interglacial cycles, in Springer Encyclopaedia of Snow, Ice and Glaciers.

Let us quote a bit:

Joseph Adhémar (1842) formulated the conjecture that the precession of Earth’s orbit caused ice ages, because of its effects on the seasonal distribution of incoming solar radiation (insolation). He realised that one season had to be critical given that the changes in winter and summer insolation caused by precession cancel each other (Herschell, 1830). James Croll (1875) further developed the theory and appreciated the importance of the three Earth orbital elements determining insolation: eccentricity, obliquity (angle between the equator and the ecliptic) and the longitude of the perihelion.

Milutin Milankovitch (1920, 1941) is quoted as the first one to have established a self-contained mathematical theory linking orbital elements to insolation, and insolation to climate changes. On a suggestion of V. Köppen, he calculated the secular evolution of the summer radiation of the northern latitude (published in Köppen and Wegener, 1925), following the hypothesis that glacial cycles are driven by the effects of changes in summer insolation on snow ablation rate during this season (the conjecture had in fact been earlier expressed by Murphy, 1876, and it contradicted Croll’s views). Summer insolation is largest when obliquity is large and/or when summer in the northern hemisphere corresponds to the time of perihelion passing. Milankovitch later substantiated the hypothesis by explicitly calculating the effects of radiation changes on the position of the snow line.

LINK

It is our attitude toward free thought and free expression that will determine our fate. There must be no limit on the range of temperate discussion, no limits on thought. No subject must be taboo. No censor must preside at our assemblies.

–William O. Douglas, U.S. Supreme Court Justice, 1952

–William O. Douglas, U.S. Supreme Court Justice, 1952