Debate settles on cause, demise of ice ages
Debate settles on cause, demise of ice agesDebate settles on cause, demise of ice ages -- report (08/06/2009)http://www.eenews.net/eenewspm/2009/08/06/3Paul Voosen, E&E reporter
Reaffirming what most scientists have long thought, a team of researchers has shown with great certainty that the Earth's periodic ice ages over the past 2.5 million years were caused by predictable "wobbles" in its rotation and axis.
The wobbles, caused primarily by the gravitational influences of larger planets like Jupiter and Saturn, caused an increase in solar radiation, which in turn led global ice levels to begin decreasing 19,000 years ago. The report, by researchers at Oregon State University and other institutions, will be published in Science tomorrow.
The ice ages were not initially caused by changes in atmospheric carbon dioxide levels or ocean temperatures, as some scientists have recently speculated. However, those processes amplified the melting that had already begun, the scientists say.
The research group used an analysis of 6,000 dates and locations of ice sheets to define when they started to melt. In so doing, they seem to have confirmed a theory first proposed more than 50 years ago.
The study hopes to give researchers a more precise understanding of the sun's radiative forces and how ice sheets melt in response.Sometime around now, the Earth should begun heading back toward another ice age, a process that would take thousands of years and could be halted by increased temperatures caused by man. Because of greenhouse gas emissions, one researcher said, the Earth has warmed as much in the past 200 years as it might normally do in several thousand years.See story:http://www.sciencedaily.com/releases/2009/08/090806141512.htm>Tim