Geologist Connects Regular Changes of Earth's Orbital Cycle to Changes in Climate

Geologist Connects Regular Changes of Earth's Orbital Cycle to Changes in Climate

ScienceDaily (Apr. 6, 2010) — In an analysis of the past 1.2 million years, UC Santa Barbara geologist Lorraine Lisiecki discovered a pattern that connects the regular changes of Earth's orbital cycle to changes in Earth's climate.

The finding is reported in the scientific journal Nature Geoscience.

Lisiecki performed her analysis of climate by examining ocean sediment cores. These cores come from 57 locations around the world. By analyzing sediments, scientists are able to chart Earth's climate for millions of years in the past. Lisiecki's contribution is the linking of the climate record to the history of Earth's orbit.

It is known that Earth's orbit around the sun changes shape every 100,000 years. The orbit becomes either more round or more elliptical at these intervals. The shape of the orbit is known as its "eccentricity." A related aspect is the 41,000-year cycle in the tilt of Earth's axis.

Glaciation of Earth also occurs every 100,000 years. Lisiecki found that the timing of changes in climate and eccentricity coincided. "The clear correlation between the timing of the change in orbit and the change in the Earth's climate is strong evidence of a link between the two," said Lisiecki. "It is unlikely that these events would not be related to one another."

Besides finding a link between change in the shape of the orbit and the onset of glaciation, Lisiecki found a surprising correlation. She discovered that the largest glacial cycles occurred during the weakest changes in the eccentricity of Earth's orbit -- and vice versa. She found that the stronger changes in Earth's orbit correlated to weaker changes in climate. "This may mean that the Earth's climate has internal instability in addition to sensitivity to changes in the orbit," said Lisiecki.

http://www.sciencedaily.com/releases/2010/04/100406133707.htm

wherever Earth climate is at this point?

on climate.

Assuming we cut out all the problems we ourselves create what would the overall affect be?

Instead with man's contributions escalating global warming, we'll see increases in violent weather, and probably a mini-ice age triggered by desalination of the north Atlantic, as well as increased desertification in the tropics.

in the Earth's orbit and shape explain what appears to be a substantial increase in geological forces such as earthquakes and, to a lesser extent, volcanoes?

This scientist hasn't connected anything at all.

Is this ScienceDaily a credible outfit? I find it strange that they would present a well known and studied science concept as if it were something new and not even credit the original term of the Milankovitch Cycle.

Lorraine E. Lisiecki1

Top of pageVariations in the eccentricity (100,000 yr), obliquity (41,000 yr) and precession (23,000 yr) of Earth’s orbit have been linked to glacial–interglacial climate cycles. It is generally thought that the 100,000-yr glacial cycles of the past 800,000 yr are a result of orbital eccentricity1, 2, 3, 4. However, the eccentricity cycle produces negligible 100-kyr power in seasonal or mean annual insolation, although it does modulate the amplitude of the precession cycle. Alternatively, it has been suggested that the recent glacial cycles are driven purely by the obliquity cycle5, 6, 7. Here I use statistical analyses of insolation and the climate of the past five million years to characterize the link between eccentricity and the 100,000-yr glacial cycles. Using cross-wavelet phase analysis, I show that the relative phase of eccentricity and glacial cycles has been stable since 1.2 Myr ago, supporting the hypothesis that 100,000-yr glacial cycles are paced8, 9, 10 by eccentricity4, 11. However, I find that the time-dependent 100,000-yr power of eccentricity has been anticorrelated with that of climate since 5 Myr ago, with strong eccentricity forcing associated with weaker power in the 100,000-yr glacial cycle. I propose that the anticorrelation arises from the strong precession forcing associated with strong eccentricity forcing, which disrupts the internal climate feedbacks that drive the 100,000-yr glacial cycle. This supports the hypothesis that internally driven climate feedbacks are the source of the 100,000-yr climate variations12.

http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo828.html

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Unfortuantely, the full text paper is not free.

I think that the important sentence is "This supports the hypothesis that internally driven climate feedbacks are the source of the 100,000-yr climate variations."

In other words, the period of climatic bistable oscillations between warm periods (e.g. now) and cold periods (most of the time) is determined by the dynamics of the earth's climate system, i.e. 100,000 years is a resonance of the earth. When the earth's climate with its resonance of 100,000 years is driven by a weak forcing at 100,000 year intervals due to ellipticity, the result is the characteristic 100,000 year long glacial periods.