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Thursday, July 23, 2015

Climate change not global per peer reviewed PNAS glacier study. Climate of Northern and Southern Hemispheres completely unconnected. Reverses earlier scientific view-University of Queensland

University of Queensland writes, "a generalised global approach isn’t the solution to climate issues." Reversing previous findings, July 2014 peer reviewed study finds "climate change not so global," Southern Hemisphere ice sheet changes are "neither synchronous with nor simply lag or lead Northern Hemisphere ice sheet records, which has important implications for the reconstruction of past interhemispheric climate linkages and mechanisms:"
 
8/4/14, "Climate change not so global," University of Queensland, Australia

"Scientists are calling for a better understanding of regional climates, after research into New Zealand's glaciers has revealed climate change in the Northern Hemisphere does not directly affect the climate in the Southern Hemisphere.

The University of Queensland study showed that future climate changes may impact differently in the two hemispheres, meaning a generalised global approach isn’t the solution to climate issues.

UQ School of Geography, Planning and Environmental Management Head Professor Jamie Shulmeister said the study provided evidence for the late survival of significant glaciers in the mountains of New Zealand at the end of the last ice age a time when other ice areas were retreating.

This study reverses previous findings which suggested that New Zealand's glaciers disappeared at the same time as ice in the Northern Hemisphere,” he said.

“We showed that when the Northern Hemisphere started to warm at the end of the last ice age, New Zealand glaciers were unaffected.

“These glaciers began to retreat several thousand years later, when changes in the Southern Ocean led to increased carbon dioxide emissions and warming.

This indicates that future climate change may impact differently in the two hemispheres and that changes in the Southern Ocean are likely to be critical for Australia and New Zealand.”

The study used exposure dating of moraines - mounds of rocks formed by glaciers - to reconstruct the rate of ice retreat in New Zealand’s Ashburton Valley after the last glacial maximum – the time when the ice sheets were at their largest.

The researchers found that the period from the last glacial maximum to the end of the ice age was longer in New Zealand than in the Northern Hemisphere.

They also found that the maximum glacier extent in New Zealand occurred several thousand years before the maximum in the Northern Hemisphere, demonstrating that growth of the northern ice sheets did not cause expansion of New Zealand glaciers.

New Zealand glaciers responded largely to local changes in the Southern Ocean, rather than changes in the Northern Hemisphere as was previously believed,” Professor Shulmeister said.

“This study highlights the need to understand regional climate rather than a global one-size-fits-all.”

The research was conducted in collaboration with the University of Griefswald, Germany, the Australian Nuclear Science and Technology Organisation, and the University of Canterbury, New Zealand, and published in the Proceedings of the National Academy of Science in July."

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Peer reviewed PNAS study cited above:

7/28/2014, "The early rise and late demise of New Zealand’s last glacial maximum," PNAS.org, Henrik Rothera,1 David Finkb, James Shulmeisterc, Charles Mifsudb, Michael Evansd, and Jeremy Pughe,2
.
"Significance"...

"This record from a key site in the midlatitude Southern Hemisphere shows that the largest glacial advance did not coincide with the coldest temperatures during this phase. We also show that the regional post-LGM ice retreat was very gradual, contrary to the rapid ice collapse widely inferred. This demonstrates that glacial records from New Zealand are neither synchronous with nor simply lag or lead Northern Hemisphere ice sheet records, which has important implications for the reconstruction of past interhemispheric climate linkages and mechanisms.".

"Abstract"

"Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the last glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models....These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early last glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka."

"This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1401547111/-/DCSupplemental." 

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