Sunday, November 4, 2012

Sandy: An Omen of Abrupt Climate Change?

Prof. Klaus Jacob of the Earth Institute at Columbia University, appearing on Chris Hayes’ UP' Saturday morning, projected that the receded shoreline of New Jersey visible today after Superstorm Sandy will become the norm by 2100 – due to rising sea levels. Either coastal cities will have to construct massive barriers or dykes such as we see in the Netherlands, or watch coastal cities inundated. His Sept. 10, 2009 prediction of a storm with surge 1’ higher than Irene was described as “prescient” by Hayes. That was:

“If the surge had been just that much higher, subway tunnels would have flooded, segments of the Franklin Delano Roosevelt Drive and roads along the Hudson River would have turned into rivers and sections of the commuter rail system would have become impassable or bereft of power….”

Reading Jacob’s words as projected on the screen conveyed an eerie feeling that we now have ‘passed through the looking glass’ and may be staring precipitous or abrupt climate change in the face – muting any further denier bilge or protests.

But what is the scientific basis?

According to Prof. Harunur Rashid, the co-Editor of an AGU (American Geophysical Union) monograph entitled 'Abrupt Climate Change: Mechanisms, Patterns and Impacts', the "defining moment for abrupt climate change research" occurred in 1993 when Willi Dansgaard and colleagues published oxygen isotope records for Greenland ice core samples that showed the air temperature swingin back and forth - meaning oscillating warming and cooling periods with time intervals as short as 1,000 years. Such temperature swings have subsequently become known as Dansgaard-Oeschger oscillations.

Though these "D-O oscillations' were first noted in Greenland ice cores, they were later observed in North Atlantic marine sediment samples. Subsequent studies disclosed abrupt climate events to be essentially ubiquitious - emerging anyplace on Earth that was subjected to sufficient study, analysis, including: Antarctica, the Pacific Ocean, the Atlantic Ocean, the Indian Ocean and on land with records captured in cave mineral deposits.

Before the D-O oscillations discovery, the general belief - grounded in paleo- oceanographic research - was that the climate was governed by the so-called "Milankovitch cycles" or forced events related to the relative positions of the Sun and Earth (e.g. the semi-major axis of Earth is believed to alter some small %) as well as the tilt of the Earth's axis which is believed to vary from 21 to 24 degrees over an approximately 41,000 year period.

The cycles are presumed to be driven by the eccentricity or the progressive alteration of orbital elements in the Earth's orbit combined with alterations in Earth's axial tilt. As Rashid has noted in an interview for EOS - the journal of the AGU (Vol. 93, No. 32, Aug. 7, 2012, p. 310):

"At the time these cycles were considered abrupt climate change but we now know that is not accurate.".

Indeed, in a blog - one of the first on Brane Space some five years ago (Dec. 5, 2007), I basically dismissed the entire notion of Milankovitch forcings Therein I showed the hypothesis actually arose in the geological rsearch community (the name comes from a Serbian engineer with an avocation of astronomy) and not the celestial mechanics - astronomy research community.

The point is, Milankovitch cycles can't explain abrupt or rapid climate change, nor do they conform to a workable hypothesis unless actual evidence for change in the orbital elements is determined from celestial mechanics principles, not deep ocean finds or conjectures based on what is really circumstantial geological evidence. In any case, as I noted, these cycles can only account for temperature differences on the order of 1-2 F whereas differences of 7-10 have been observed.

The primary mechanism for abrupt climate change? According to Rashid (op. cit.):

"If you polled climatologists, probably 99% of them would agree that the interaction between freshwater in the North Atlantic and the Atlantic Meriodonal Overturning Circulation (AMOC) is the biggest driver of abrupt climate change."

The critical tipping point for inundating cities on the east coast? Likely when enough atmospheric CO2 is added such that the concentrations induce even more Arctic sea ice melting - to which massive fresh water runoff is added (from the repeatedly freezing and thawing northern continents such as Siberia, northern Canada.) These, according to Rashid, can disturb the AMOC with the result that the temperature balance is upset between the northern and southern hemispheres.

It is then possible that the predictions made by Klaus Jacob will come to pass. More research needs to be done, but for sure 'Sandy' and its aftermath is a heads up. As Prof. Jacobs noted, we need to either invest in protecting our cities and coastlands now....or reap the whirlwind later.

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