On Jan 29, 7:00*am, wrote:
How 450mn-yr-old mass extinction is closely linked to climate change

2011-01-28
ANI

Geobiologists at California Institute of Technology have found how the mass
extinction that occurred 450 mn y ago is linked to a cooling climate.

The mass extinction coincided with a glacial period, during which global
temperatures cooled and the planet saw a marked increase in glaciers.

So the team studied the timing and magnitude of the glaciation and how it
affected ocean temperatures near the equator

ø I am extremely skeptical about this article.
It seems to be a yarn to support the AGW
funding, and so far away as to be irrelevant
to conditions today.

ø The fact today is that we have here is an ice
age that ended 12 to 15,000 years ago. The
10,000 year interglacial ended about 1,500
years ago. We are now at the end of the
trend to glaciation. Expect the Polar ice begin
inching toward the Equator bet 2020 and 2050.

Don't expect to see the ice in your
grandchildren's or your great great
grandchildren's time.

It takes much longer to freeze than to melt.
Perhaps in 15,000+ years might reach the
Ice's extent or it might take longer. We have
sufficient time to prepare.








"Our observations imply a climate system distinct from anything we know about
over the last 100 million years," said Woodward Fischer.

However, "one of the biggest sources of uncertainty in studying the
paleoclimate record is that it's very hard to differentiate between changes in
temperature and changes in the size of continental ice sheets," said Seth
Finnegan.

Both factors are equally plausible in having caused the mass extinction but
differentiating between the two effects is a challenge because until now, the
best method for measuring ancient temperatures has also been affected by the
size of ice sheets.

Using a new type of paleothermometer the team developed, the researchers have
determined the average temperatures during the Late Ordovician-the first time
they have been able to tide over the issue.

"By providing independent information on ocean temperature, this new method
allows us to know the isotopic composition of 450-million-year-old seawater,"
Finnegan said.

"Using that information, we can estimate the size of continental ice sheets
through this glaciation."

And eventually, the researchers can learn more about what Ordovician climate
was like-and how it might have stressed marine ecosystems and led to the
extinction.

The team discovered that even though tropical ocean temperatures were higher
than they are now, moderately sized glaciers still existed near the poles
before and after the mass extinction. But during the extinction intervals,
glaciation peaked.

Tropical surface waters cooled by 5 C, and the ice sheets on Gondwana
grew to be as large as 150 mn km3 - bigger than the glaciers
that covered Antarctica and most of the Northern Hemisphere during the modern
era's last ice age 20k y ago.

"Although polar glaciers existed for several million years, they only caused
cooling of the tropical oceans during the short interval that coincides with
the main pulse of mass extinction," Finnegan said.