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Science Forum Index » Environment Forum » Debate Over Temperatures Heats Up
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| David Naugler |
 Posted: Fri Dec 19, 2003 10:14 am |
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From:
http://www.techcentralstation.com/121903D.html
Debate Over Temperatures Heats Up
By George Taylor Published 12/19/2003
A recent Associated Press article suggested that humans have been
changing the global climate since thousands of years before the
industrial revolution. 8,000 years ago atmospheric levels of carbon
dioxide began to rise as humans began clearing forests, planting crops
and raising livestock, according to the article. Methane levels
started increasing 3,000 years later.
The scientist quoted in the article was Bill Ruddiman, emeritus
professor at the University of Virginia. Ruddiman suggested that the
human-caused disruption would have been sufficient to create much
warmer climate during ancient times than "natural" conditions would
have suggested.
Right now there is a raging debate occurring regarding the
temperatures of the last several thousand years. The longstanding
view, championed by H.H. Lamb and other climate historians, was that
the Holocene (the pleasant interglacial period in which civilization
has flourished since the last Ice Age 15,000 years ago) has been
marked by several notable climate fluctuations:
1. a very warm period about 3,000 B.C., the warmest of the Holocene
(the "Holocene Maximum";
2. a gradual cooling thereafter, reaching a low point around the time
of Christ;
3. a warming for about 1,000 years, peaking in roughly 1,000 A.D.
("Medieval Warm Period")
4. a cooling for several hundred years, with the coldest period from
about 1560-1830 ("Little Ice Age")
5. brief warm and cool periods from 1830-1870 and 1870-1910,
respectively
6. a warmer 20th century, for the most part.
On shorter scales (decades or less) there have been numerous rises and
falls in temperatures, some of them quite significant, but the
long-term changes are those listed above.
Lamb and other historians using various recorded and anecdotal
information concluded that the Medieval Warm Period temperatures were
comparable to those of modern times, the Holocene Maximum was much
warmer, and the little Ice Age was much cooler.
Enter Michael Mann of the University of Virginia, lead author of a
paper that presented a much different viewpoint. Using tree ring and
other data for estimating temperature histories back to 1,000 AD, Mann
created a new and very different history. The Medieval Warm Period no
longer existed, scarcely distinguishable from the Little Ice Age.
Suddenly our current temperatures had become "the highest in 1,000
years." This was proof, so it was claimed, that human-induced global
warming was occurring!
One of the most valuable and heavily-referenced "paleoclimate data
sets" (data used to infer long-term climate change) is the Vostok ice
core data. In January 1998, a collaborative ice-drilling project
between Russia, the United States, and France at the Russian Vostok
station in East Antarctica yielded the deepest ice core ever
recovered, reaching a depth of 3,623 m (nearly 12,000 feet). The ice
was deposited in layer upon layer, like dirt where the Grand Canyon
intersects, each representing a year. The lowest layers were deposited
about 400,000 years ago.
Ice cores are valuable because they contain tiny gas bubbles whose
composition can be measured. CO2 is measured directly using a gas
chromatograph, while temperature is estimated from concentrations of
two gases, deuterium and Oxygen-18.
Early Vostok data analysis looked at samples centuries apart, and
concluded (correctly) that there is a very strong relationship between
temperatures and CO2 concentrations. The conclusion for many was
obvious: when CO2 goes up, temperatures go up, and vice-versa. This
became the basis for a number of scary-looking graphs in books by the
scientist Stephen Schneider, former Vice President Al Gore, and
others, predicting a much warmer future (since most scientists agree
that CO2 will continue to go up for some time).
Well, it's not as simple as that. When the Vostok data were analyzed
for much shorter time periods (decades at a time rather than
centuries), something different emerged. H. Fischer and coauthors
reported in Science (283: 1712-1714, 1999) that "the time lag of the
rise in CO2 concentrations with respect to temperature change is on
the order of 400 to 1000 years." In other words, CO2 changes are
caused by temperature changes! Many other recent studies have shown
similar results. Studies by Indermuhle et al (2000), Monnin et al
(2001), and Mudelsee et al (2001) indicated a lag of 800-1500 years
between temperature and CO2. References are available on request.
Ruddiman's study is interesting, and bears further analysis. But two
counter-arguments stand out: it is unlikely that the rather low human
populations of ancient times would have had the means to produce such
high CO2 levels, aside from massive forest fires; and the high
"spikes" in CO2 were more likely responses to the abrupt warm periods
which are known to have existed. Warm periods would have triggered
increases in plant life, which eventually would have died or been
burned and released to the atmosphere -- as CO2. Warmer ocean
temperatures would have released CO2 to the atmosphere (more CO2 is
absorbed when water is cooler).
And why would temperature have risen and fallen if CO2 were not to
blame? It's anyone's guess -- but my guess is that changes in earth's
orbit, solar activity and ocean circulation were chiefly responsible
for the warm and cool periods.
George H. Taylor, Oregon State Climatologist. Email him at
taylorgh@comcast.net |
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| Vendicar Decarian |
| Posted: Sat Dec 20, 2003 10:07 am |
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"David Naugler" <dnaugler@sfu.ca> wrote in message
news:c6bcfffa.0312190714.46974e14@posting.google.com...
The three attached pictures provide all of the information required. |
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| James |
| Posted: Sun Dec 21, 2003 12:42 pm |
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| H. Dziardziel |
| Posted: Sun Dec 21, 2003 3:12 pm |
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| Vendicar Decarian |
| Posted: Sun Dec 21, 2003 6:14 pm |
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"James" <jrapier@dcr.net> wrote in message news:0%kFb.15$im3.5@fe01...
Quote: http://www.math.duke.edu/~haase/MISC/courseOfScience.html
Three attached pictures to educate James. |
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| Vendicar Decarian |
| Posted: Sun Dec 21, 2003 7:48 pm |
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"H. Dziardziel" <hdzi@zworg.nospamcom> wrote in message
news:5kvbuvkidjenug27r1ovg40n77faeklvav@4ax.com...
Analysis of Possible Human Contributions to Global Warming
Report for Chemistry 1A, Experiment 1 by A. Student. |
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| Roger Coppock |
| Posted: Mon Dec 22, 2003 2:59 pm |
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Vendicar Decarian wrote:
You can't educate the permanently uninfomed, Vendicar.
--
"One who joyfully guards his mind
And fears his own confusion
Can not fall.
He has found his way to peace."
-- Buddha, in the "Pali Dhammapada,"
~5th century BCE
-.-. --.- Roger Coppock (rcoppock@adnc.com)
-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
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| Vendicar Decarian |
| Posted: Tue Dec 23, 2003 12:50 am |
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"Roger Coppock" <rcoppock@adnc.com> wrote in message
news:3FE74D27.93564B1B@adnc.com...
Quote: You can't educate the permanently uninfomed, Vendicar.
As I often say about the permanently ignorant. Death will be their only
release. |
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| James |
| Posted: Tue Dec 23, 2003 11:08 pm |
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"Vendicar Decarian" <VD@Pyro.net> wrote in message
news:GJQFb.28675$mV5.686@read1.cgocable.net...
Quote:
"Roger Coppock" <rcoppock@adnc.com> wrote in message
news:3FE74D27.93564B1B@adnc.com...
You can't educate the permanently uninfomed, Vendicar.
As I often say about the permanently ignorant. Death will be their only
release.
Thank you Ian. |
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