The Sun, Not CO2, Caused Ice Age Glaciers To Melt

Submitted by Doug L. Hoffman on Sun, 08/09/2009 - 16:32

Increased insolation 20,000 years ago caused deglaciation in the Norther Hemisphere, according to a new report in the August 7, 2009, edition of Science. Further more, it was the onset of deglaciation of the West Antarctic Ice Sheet, which occurred between 14 - 15 thousand years ago, that was the source of sea-level rise at the beginning of the Holocene warming. Such events are often associated with rising CO₂ levels by climate catastrophists but the evidence says otherwise.

The Last Glacial Maximum (LGM) is typically defined as the most recent interval in Earth history when global ice sheets reached their maximum volume. This is conventionally calculated from sea-level records but, according to Peter U. Clark et al. this is an overly simplistic approach. Sea-level records do not distinguish between globally synchronous ice-sheet maxima and temporary regional ice-sheet maxima that can combine to produce apparent sea-level low points that can last for a thousand years or more. In their report the author's describe their improved approach as follows:

We drew on 4271 ¹⁴C ages and 475 terrestrial cosmogenic nuclide (TCN) ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of maxima in global ice-sheet extent. For all but the Barents-Kara and Greenland Ice Sheets, the spatial distribution of ages is sufficient to evaluate regional variability in the timing of maxima for different sectors of individual ice sheets. Because ice-sheet extent scales with ice volume, our constraints on regional variability in ice-sheet maxima allow us to evaluate the temporal evolution of individual ice-sheet contributions to global sea-level change. Because mountain glaciers are highly sensitive to climate change, we used an additional 172 ¹⁴C ages and 786 TCN ages to constrain mountain-glacier fluctuations from five widely distributed regions of the world, allowing a more comprehensive assessment of the response of the cryosphere to climate change.

The sea-level change at a number of the sites studied reflected relative changes in sea-level and not the change on a global basis. This is because of the variations in Earth's gravitational field, deformation of the planet's crust, and rotational effects on local sea levels driven by the shift of water mass from glacial ice to the ocean. “In order to evaluate these effects, we used a state-of-the-art theory that includes a realistic glaciation phase to predict the RSL change at these far-field sites,” states the report. From these up-to-date theoretical constraints a new model was built to predict the actual LGM.

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