Beam me to Planet Gore !
Posted on 06/20/2009 9:22:50 PM PDT by neverdem
The reason why those cold spells now come less frequently is still unknown
Scientists have peered back in time with a new analytical technique to see atmospheric concentrations of carbon dioxide more than 2 million years into the past. The findings indicate that a long-term decline in the levels of that greenhouse gas isn’t to blame for a geologically recent shift in the frequency of ice ages, scientists say.
The record of ice ages in North America stretches back 2.4 million years (SN: 2/5/05, p. 94). Until about 1.2 million years ago, ice ages in the Northern Hemisphere occurred about every 40,000 years, says Jerry F. McManus, a paleoclimatologist at Lamont-Doherty Earth Observatory in Palisades, N.Y. But for the past 500,000 years or so, ice ages have occurred, on average, only once every 100,000 years, he notes.
Several explanations for this shift have been proposed, but one of the most popular ones — a long-term decline in carbon dioxide levels — isn’t to blame, McManus and his colleagues suggest in the June 19 Science.
By chemically analyzing air bubbles trapped in ice, researchers can get a direct measurement of atmospheric composition. But so far, the longest ice core available reaches back only 800,000 years, McManus says. So, he and his colleagues sought a technique that could look back further into time — one that could take advantage of the multimillion-year records available in seafloor sediments.
The team’s lab tests indicate that the ratio of boron-11 and boron-12 isotopes incorporated from seawater into the calcium carbonate shells of a marine microorganism called Globigerinoides sacculifer depends on the pH of the water in which the creatures lived. That pH, in turn, depends on the concentration of carbon dioxide in the air, because the gas forms an acid when it dissolves in water...
(Excerpt) Read more at sciencenews.org ...
Bump for reference...
Ping for later reading
Thanks for the post.
Oooohh - someone's gonna lose their magic decoder ring!
No one crosses the Goreacle!
The debate is over, why bring this up...
The Goreacle couldn't (gasp!) be...wrong...could he?
Prostate Cancer: From Inoperable to Cancer Free
Team Detects High-Speed Hydrogen Atoms Coming From the Moon
FReepmail me if you want on or off my health and science ping list.
From the abstract:
“...estimates are consistent with a close linkage between atmospheric CO2 concentration and global climate, but the lack of a gradual decrease in interglacial PCO2 does not support the suggestion that a long-term drawdown of atmospheric CO2 was the main cause of the climate transition.”
Of course, we know that ice is an absolutely impermeable material. What hogwash.
You can argue with proxy data, but you can't say it is not frozen in place. What the author does do is undermine carbon dioxide as a driving force causing climate change. This data supports the idea that carbon dioxide is a lagging indicator of prior climate change.
ping
Until about 1.2 million years ago, ice ages in the Northern Hemisphere occurred about every 40,000 years, says Jerry F. McManus, a paleoclimatologist at Lamont-Doherty Earth Observatory in Palisades, N.Y. But for the past 500,000 years or so, ice ages have occurred, on average, only once every 100,000 years, he notes.Thanks neverdem.
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Thanks neverdem.Until about 1.2 million years ago, ice ages in the Northern Hemisphere occurred about every 40,000 years, says Jerry F. McManus, a paleoclimatologist at Lamont-Doherty Earth Observatory in Palisades, N.Y. But for the past 500,000 years or so, ice ages have occurred, on average, only once every 100,000 years, he notes.To all -- please ping me to other topics which are appropriate for the GGG list. |
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Historic Variation in Arctic Ice
Watts Up With That? | Jun 20, 2009 | Tony B
Posted on 06/20/2009 2:16:27 PM PDT by decimon
http://www.freerepublic.com/focus/bloggers/2275979/posts
So if the old time line was correct we’d be due for a new ice age at any point, with the new one we would have over 60,000 years to wait.
Global Warming on Free Republic
That's one way to say it. The other is that the warm inter-glacial periods used to show up every 40,000 years and now it's every 100,000 years. It isn't that cold isn't arriving so often, it's that the cold stays around so much longer when it is here.
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