Saturday, August 25, 2007

Younger Dryas Climate Tipping Point Tossed in Bin

The Younger Dryas occurred as an Ice Age was ending. As the climate began to warm, a huge and sudden rush of fresh meltwater broke out from the Great Lakes and swept out to sea. The water surge was monumental enough that the meltwater lowered the salinity of the ocean, shut down the Atlantic conveyor currents, which disperse the planet's heat, and threw the northern hemisphere back into another thousand years of Ice Age. It raised temperatures near Greenland by a startling 15 degrees C, even as it doubled annual rainfall.

Modern climatologists have savored the Younger Dryas event as massive evidence of what comes when we push the planet's climate too close to a "tipping point." Further human-driven warming, they say, will make such abrupt climate changes more likely, with searing droughts, torrential rainfall, and extreme heat.

The National Academy of Sciences issued a 2002 report titled Abrupt Climate Change: Inevitable Surprises, which said abrupt climate changes have been especially common when the climate system was being forced to change most rapidly. According to that theory, greenhouse warming today could be drastically increasing risks from climate change.

Arbitary assumptions from the “model makers” and their creationist theories of a “steady state planet”

The NSF have released an interesting article on a ‘Hammer of God” event that provides evidence that the model makers are wrong and an “extraterrestrial event” in the form of a comet was the precursor event.

New scientific findings suggest that a large comet may have exploded over North America 12,900 years ago, explaining riddles that scientists have wrestled with for decades, including an abrupt cooling of much of the planet and the extinction of large mammals.

The discovery was made by scientists from the University of California at Santa Barbara and their colleagues. James Kennett, a paleoceanographer at the university, said that the discovery may explain some of the highly debated geologic controversies of recent decades.

The period in question is called the Younger Dryas, an interval of abrupt cooling that lasted for about 1,000 years and occurred at the beginning of an inter-glacial warm period. Evidence for the temperature change is recorded in marine sediments and ice cores.

According to the scientists, the comet before fragmentation must have been about four kilometers across, and either exploded in the atmosphere or had fragments hit the Laurentide ice sheet in northeastern North America.

Wildfires across the continent would have resulted from the fiery impact, killing off vegetation that was the food supply of many of larger mammals like the woolly mammoths, causing them to go extinct.

Since the Clovis people of North America hunted the mammoths as a major source of their food, they too would have been affected by the impact. Their culture eventually died out.

The scientific team visited more than a dozen archaeological sites in North America, where they found high concentrations of iridium, an element that is rare on Earth and is almost exclusively associated with extraterrestrial objects such as comets and meteorites.

They also found metallic microspherules in the comet fragments; these microspherules contained nano-diamonds. The comet also carried carbon molecules called fullerenes (buckyballs), with gases trapped inside that indicated an extraterrestrial origin.

The team concluded that the impact of the comet likely destabilized a large portion of the Laurentide ice sheet, causing a high volume of freshwater to flow into the north Atlantic and Arctic Oceans.

"This, in turn, would have caused a major disruption of the ocean's circulation, leading to a cooler atmosphere and the glaciation of the Younger Dryas period," said Kennett. "We found evidence of the impact as far west as the Santa Barbara Channel Islands."

Of course we have nothing to worry about as near-Earth objects (NEOs) have been detected, primarily by ground-based optical searches, in the size range between 10 meters and 30 kilometers, out of a total estimated population of about one million; some information about the physical size and composition of these NEOs is available for only 300 objects. The total number of objects a kilometer in diameter or larger, a size that could cause global catastrophe upon Earth impact, is now estimated to range between 900 and 1,230.


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