Tuesday, May 24, 2011

Hyper-thermal Earth






This is a rather important issue and what we have is geological evidence whose level of resolution is in the order of ten millennia at a crack.  Then we assume some form of continuity and end up producing nonsense.  I am not sure what these long periods of climates been warmer by 2 to 3 degrees actually mean, but the one mechanism able to do this is the positioning of a polar ice cap that survives.  The actual cooling range also conforms to our expectations.

It needs to be remembered that Ice Age Earth was the result of two fully emplaced polar ice caps and the blockage of a substantial part of the equatorial current.  One could hardly design a worse situation.  This ended by preserving the South Polar Cap while engaging the Gulf Stream to end the North Polar Cap.  It is my conjecture that this was done deliberately for this exact purpose (it was really too good to be an accident) and that the resultant Holocene is good for millions of year if not until the Pacific itself is subsumed.

Of course, current scholarship prefers to accept the curious idea that the Ice Age penetrated in full into the lower latitudes, when that naturally is impossible without creating Ice Ball Earth.  In fact all the main arguments against an Ice Age from the nineteenth century never were resolved and have simply been forgotten in the face of overwhelming evidence of simple existence.  The fact is that simply rotating the crust so that the North Pole is at thirty degrees south in Hudson Bay makes all those nineteenth century objections and a lot more besides simply disappear because the entirety if the purported Ice Age is then actually in the appropriate fifteen degrees of the poles is and was Antarctica.

It is reasonable that a large land mass passing through a pole would accumulate an ice cap that may well be vulnerable to melt outs.  This would be able to adjust temperatures by the expected range on the geological time scale proposed.  It is useful to think of such caps as the temperature control device that can be adjusted by many other possible events from magma flows elsewhere to asteroid impacts anywhere.



Ancient 'hyperthermals' guide to anticipated climate changes

Bursts of intense global warming that have lasted tens of thousands of years have taken place more frequently throughout history than previously believed, according to researchers in the US.


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In a paper published in Nature, researchers from the Scripps Institution of Oceanography at the University of California San Diego and colleagues from the UK, Germany and Spain, report that releases of carbon dioxide sequestered in the deep oceans were the most likely trigger of these ancient "hyperthermal" events.

Most of the events raised average global temperatures between 2 and 3 °C, an amount comparable to current conservative estimates of how much temperatures are expected to rise in coming decades as a consequence of anthropogenic global warming. Most hyperthermals lasted about 40,000 years before temperatures returned to normal.

"These hyperthermals seem not to have been rare events," says Richard Norris from Scripps. "Hence there are lots of ancient examples of global warming on a scale broadly like the expected future warming. We can use these events to examine the impact of global change on marine ecosystems, climate and ocean circulation."

The hyperthermals took place roughly every 400,000 years during a warm period of Earth's history that prevailed some 50 million years ago. The strongest of them coincided with an event known as the Paleocene–Eocene Thermal Maximum, the transition between two geologic epochs in which global temperatures rose between 4 and 7 °C and needed 200,000 years to return to historical norms. The events stopped taking place around 40 million years ago, when the planet entered a cooling phase. No warming events of the magnitude of these hyperthermals have been detected in the geological record since then.

Phil Sexton, a former student of Norris' now at the Open University, UK, led the analysis of sediment cores collected off the South American coast. In the cores, evidence of the warm periods presented itself in bands of grey sediment layered within otherwise pale-greenish mud. The grey sediment contained increased amounts of clay left after the calcareous shells of microscopic organisms were dissolved on the sea floor. These clay-rich intervals are consistent with ocean acidification episodes that would have been triggered by large-scale releases of carbon dioxide. Large influxes of carbon dioxide change the chemistry of seawater by producing greater amounts of carbonic acid in the oceans.

The authors concluded that a release of carbon dioxide from the deep oceans was a more likely cause of the hyperthermals than other triggering events that have been hypothesized. The regularity of the hyperthermals and relatively warm ocean temperatures of the period makes them less likely to have been caused by events such as large melt-offs of methane hydrates, terrestrial burning of peat or even proposed cometary impacts. The hyperthermals could have been set in motion by a build-up of carbon dioxide in the deep oceans caused by slowing or stopping of circulation in ocean

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