Friday, December 02, 2011 7:32:14 PM
CO2 plunge linked to Antarctic freeze
The finding strengthens the link between CO2 levels and global temperature
(Source: Joe Mastroianni/National Science Foundation)
Stuart Gary
ABC
Friday, 2 December 2011
Scientists have linked a dramatic fall in carbon dioxide levels in the atmosphere with the formation of the Antarctic ice cap, 34 million years ago.
The new findings, reported in the journal Science [ http://www.sciencemag.org/content/334/6060/1261 ( http://dx.doi.org/10.1126/science.1203909 )], show how closely carbon dioxide levels are linked to major climatic changes.
Dr Willem Sijp of the Climate Change Research Centre [ http://www.ccrc.unsw.edu.au/ ] at the University of New South Wales, says their research found atmospheric CO2 levels plunged by 40 per cent over a three million year period before and during the formation of the Antarctic ice sheet.
"The new report contradicts earlier work based on rock samples from the Southern Ocean apparently showing carbon dioxide levels were climbing while Antarctica was freezing over," says Sijp.
He says the new research factored in continental drift, which changed wind and ocean currents, as well as changes in the Earth's orbit.
"Earlier temperature estimates didn't take these into account, leading to inflated numbers showing increasing levels of carbon dioxide when in reality they were actually decreasing," says Sijp.
The research examined drill core samples looking at carbon isotope ratios in algae that died and fell to the sea floor 34 million years ago.
According to Sijp, changes in Southern Ocean currents and conditions meant temperatures were different and nutrient loads lower, directly affecting the algae and changing the inferred carbon dioxide levels.
"When we re-calculated atmospheric CO2, we found Antarctica's big freeze followed a fall in carbon dioxide levels," he says.
Colder Earth
Antarctic glaciation occurred during a geologic period called the Eocene to Oligocene climate transition.
"It was a time of dramatic changes triggered during a cold orbital cycle when precession of the Earth's axis and changes in its orbit aligned to make southern hemisphere summers colder," says Sijp.
"This allowed icesheets to survive year round and gradually increase in altitude as fresh snow and ice was added. As the altitude increased, the surrounding air got colder, which further aided in cooling, creating a positive feedback loop."
"At the same time continental drift ... allowed the creation of the Antarctic circumpolar current which also had a significant cooling effect on Antarctica."
Sijp says the growth of ice sheets also increased the Earth's albeo reflecting more of the Sun's energy back into space.
"But the main driver seems to be carbon dioxide, because that dropped 40 per cent over a three million year period as the planet cooled and Antarctica's ice sheets grew."
© 2011 ABC
http://www.abc.net.au/science/articles/2011/12/02/3381495.htm
===
Greenhouse gases to overpower ozone hole in the coming decades
As the influence of the ozone hole on the SAM decreases and greenhouse gases increase, dramatic shifts in climate are expected across Antarctica and many regions of the mid-latitude the Southern Hemisphere.
03 November 2011
One set of human-created gases is starting to relinquish its hold on Antarctic climate as another group of human emissions is starting to take hold, according to a paper in Nature Geoscience, co-authored by ARC Laureate Fellow Professor Matthew England, -co-director of the UNSW Climate Change Research Centre.
The review paper highlights how the influence on Southern Hemisphere climate of the Antarctic ozone hole is slowly dissipating and will be progressively overtaken by human-induced emissions of carbon dioxide and other greenhouse gases.
Research into the ozone hole has shown that it has had a profound impact on Southern Hemisphere climate. This has directly affected rainfall, wind speeds and temperatures over an area that ranges from Antarctica to the mid-latitude regions of the Southern Hemisphere.
"Our study shows how ozone depletion over the past three to four decades has had a marked impact on Antarctic and Southern Ocean climate,” says Professor England, who is also a Chief Investigator in the ARC centre of Excellence for Climate System Science.
“However, this will shortly be overwhelmed by the influence of greenhouse gases."
The ozone hole has significantly transformed the Southern Annular Mode (SAM), which sets the latitude of the Southern Hemisphere jet stream and storm track, and has a profound influence on the oceans.
The ozone-induced changes in the SAM have been linked to cooler than average temperatures over East Antarctica and higher than normal summer temperatures over Patagonia and the northern Antarctic Peninsula.
Further north, it has been identified as leading to higher mountain-related rainfall on the eastern side of New Zealand’s Southern Alps and the south east coast of Tasmania. At the same time this has led to less rainfall over western Tasmania and west of New Zealand’s Southern Alps and higher than normal summer temperatures in New Zealand.
As the influence of the ozone hole on the SAM decreases and greenhouse gases increase, dramatic shifts in climate are expected across Antarctica and many regions of the mid-latitude the Southern Hemisphere.
"Ozone depletion was an unintended consequence of global CFC emissions during the 20th Century, with pervasive impacts on our climate system,” Professor England said.
“This highlights how human activity can strongly alter atmospheric chemistry and how this, in turn, impacts the Earth’s radiation balance; altering natural systems now and into the future.
“Unfortunately, carbon dioxide resides in the atmosphere for many hundreds or perhaps thousands of years, unlike CFCs that decline over just decades. So, while the ozone hole will repair over the coming decades, the legacy of our emissions of carbon dioxide is still likely to be felt 1,000 years from now”.
Copyright © University of New South Wales
http://www.ccrc.unsw.edu.au/news/news/2011-11-03_ozonehole.html
===
(linked in) http://investorshub.advfn.com/boards/read_msg.aspx?message_id=69558601 and preceding (and any future following)
The finding strengthens the link between CO2 levels and global temperature
(Source: Joe Mastroianni/National Science Foundation)
Stuart Gary
ABC
Friday, 2 December 2011
Scientists have linked a dramatic fall in carbon dioxide levels in the atmosphere with the formation of the Antarctic ice cap, 34 million years ago.
The new findings, reported in the journal Science [ http://www.sciencemag.org/content/334/6060/1261 ( http://dx.doi.org/10.1126/science.1203909 )], show how closely carbon dioxide levels are linked to major climatic changes.
Dr Willem Sijp of the Climate Change Research Centre [ http://www.ccrc.unsw.edu.au/ ] at the University of New South Wales, says their research found atmospheric CO2 levels plunged by 40 per cent over a three million year period before and during the formation of the Antarctic ice sheet.
"The new report contradicts earlier work based on rock samples from the Southern Ocean apparently showing carbon dioxide levels were climbing while Antarctica was freezing over," says Sijp.
He says the new research factored in continental drift, which changed wind and ocean currents, as well as changes in the Earth's orbit.
"Earlier temperature estimates didn't take these into account, leading to inflated numbers showing increasing levels of carbon dioxide when in reality they were actually decreasing," says Sijp.
The research examined drill core samples looking at carbon isotope ratios in algae that died and fell to the sea floor 34 million years ago.
According to Sijp, changes in Southern Ocean currents and conditions meant temperatures were different and nutrient loads lower, directly affecting the algae and changing the inferred carbon dioxide levels.
"When we re-calculated atmospheric CO2, we found Antarctica's big freeze followed a fall in carbon dioxide levels," he says.
Colder Earth
Antarctic glaciation occurred during a geologic period called the Eocene to Oligocene climate transition.
"It was a time of dramatic changes triggered during a cold orbital cycle when precession of the Earth's axis and changes in its orbit aligned to make southern hemisphere summers colder," says Sijp.
"This allowed icesheets to survive year round and gradually increase in altitude as fresh snow and ice was added. As the altitude increased, the surrounding air got colder, which further aided in cooling, creating a positive feedback loop."
"At the same time continental drift ... allowed the creation of the Antarctic circumpolar current which also had a significant cooling effect on Antarctica."
Sijp says the growth of ice sheets also increased the Earth's albeo reflecting more of the Sun's energy back into space.
"But the main driver seems to be carbon dioxide, because that dropped 40 per cent over a three million year period as the planet cooled and Antarctica's ice sheets grew."
© 2011 ABC
http://www.abc.net.au/science/articles/2011/12/02/3381495.htm
===
Greenhouse gases to overpower ozone hole in the coming decades
As the influence of the ozone hole on the SAM decreases and greenhouse gases increase, dramatic shifts in climate are expected across Antarctica and many regions of the mid-latitude the Southern Hemisphere.
03 November 2011
One set of human-created gases is starting to relinquish its hold on Antarctic climate as another group of human emissions is starting to take hold, according to a paper in Nature Geoscience, co-authored by ARC Laureate Fellow Professor Matthew England, -co-director of the UNSW Climate Change Research Centre.
The review paper highlights how the influence on Southern Hemisphere climate of the Antarctic ozone hole is slowly dissipating and will be progressively overtaken by human-induced emissions of carbon dioxide and other greenhouse gases.
Research into the ozone hole has shown that it has had a profound impact on Southern Hemisphere climate. This has directly affected rainfall, wind speeds and temperatures over an area that ranges from Antarctica to the mid-latitude regions of the Southern Hemisphere.
"Our study shows how ozone depletion over the past three to four decades has had a marked impact on Antarctic and Southern Ocean climate,” says Professor England, who is also a Chief Investigator in the ARC centre of Excellence for Climate System Science.
“However, this will shortly be overwhelmed by the influence of greenhouse gases."
The ozone hole has significantly transformed the Southern Annular Mode (SAM), which sets the latitude of the Southern Hemisphere jet stream and storm track, and has a profound influence on the oceans.
The ozone-induced changes in the SAM have been linked to cooler than average temperatures over East Antarctica and higher than normal summer temperatures over Patagonia and the northern Antarctic Peninsula.
Further north, it has been identified as leading to higher mountain-related rainfall on the eastern side of New Zealand’s Southern Alps and the south east coast of Tasmania. At the same time this has led to less rainfall over western Tasmania and west of New Zealand’s Southern Alps and higher than normal summer temperatures in New Zealand.
As the influence of the ozone hole on the SAM decreases and greenhouse gases increase, dramatic shifts in climate are expected across Antarctica and many regions of the mid-latitude the Southern Hemisphere.
"Ozone depletion was an unintended consequence of global CFC emissions during the 20th Century, with pervasive impacts on our climate system,” Professor England said.
“This highlights how human activity can strongly alter atmospheric chemistry and how this, in turn, impacts the Earth’s radiation balance; altering natural systems now and into the future.
“Unfortunately, carbon dioxide resides in the atmosphere for many hundreds or perhaps thousands of years, unlike CFCs that decline over just decades. So, while the ozone hole will repair over the coming decades, the legacy of our emissions of carbon dioxide is still likely to be felt 1,000 years from now”.
Copyright © University of New South Wales
http://www.ccrc.unsw.edu.au/news/news/2011-11-03_ozonehole.html
===
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