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The Mad Monk
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of Ice Cream
Mar 2000
time: 23:32
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...a very, very long time.
It's a "good thing".
quote:
'Prehistoric man began global warming'
Date: December 11 2003
Measurements of ancient air bubbles trapped in Antarctic ice offers evidence that humans have been changing the global climate since thousands of years before the industrial revolution.
From 8000 years ago, atmospheric levels of carbon dioxide began to rise as humans started clearing forests, planting crops and raising livestock, a scientist said on Tuesday. Methane levels started increasing 3000 years later.
The combined increases of the two greenhouse gases implicated in global warming were slow but steady and staved off what should have been a period of significant natural cooling, said Bill Ruddiman, emeritus professor at the University of Virginia.
The changes also disrupted regular patterns that dominated the 400,000 years of atmospheric history that scientists have teased from samples of ancient ice.
"You have 395,000 years of history, which sets some rules, and 5000 years that break those rules," Professor Ruddiman said.
He briefed reporters on his theory at the autumn meeting of the American Geophysical Union on Tuesday. Further details appear in the December issue of the journal Climatic Change.
Previously, scientists assumed widely it was only with the onset of the factory age that human activity had any significant effect on the global climate. The prehistoric changes in carbon dioxide and methane levels have been noted before but were attributed to natural causes, Professor Ruddiman said.
"It's a great new idea we need to talk about and evaluate," said Bette Otto-Bliesner, a paleoclimate expert at the National Centre for Atmospheric Research, who was not connected with the research.
Atmospheric levels of carbon dioxide and methane naturally fluctuate, in part because of changes in the orbit of the Earth and the resulting variations in the amounts of sunlight.
But human activity apparently thwarted expected decreases in the atmospheric concentrations of both gases.
Leading the change was the revolutionary adoption, across both Europe and Asia, of agriculture and animal husbandry, Professor Ruddiman said.
Analysis of air trapped in ice cores drilled from the Antarctic ice sheet show anomalous increases in carbon dioxide levels beginning 8000 years ago - just as crop lands began to replace previously forested regions across Asia and Europe.
About 5000 years ago, the ice cores reflect a similarly anomalous rise in methane levels, this time tied to increased emissions from flooded rice fields, as well as burgeoning numbers of livestock, Professor Ruddiman said.
The prehistoric practices apparently overrode a build-up of ice that models predict should have occurred from 5000 years ago.
AP
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http://www.smh.com.au/text/articles...0732281706.html
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Berzerker
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topeka, kansas,USA
May 1999
time: 23:32
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quote:
No, what it's saying is that, at the point where past episodes indicated there should be a (pre-ice age) reduction in gases, this most recent period shows a continued increase. |
These gases always increase during interglacial periods and these gases continue increasing until whatever causes a new ice advance gets triggered. I don't have my graphs handy but interglacial periods can last as little as ~6-7 thousand years up to ~15,000 years. It's been roughly 13-14 thousand years since the end of the last ice advance so I'm not concerned with "global warming" but with what will trigger the next advance of the ice sheets. I'm hoping human activity does help negate the trigger but I suspect the trigger is far beyond our control.
It has been said ice advances have several orbital phenomenon coming together to decrease summer sunlight to the higher (northern) latitudes resulting in less snow melt during the summer months which in turn results in more snow remaining on the ground heading into winter.
The orbital tilt of the Earth is one of these phenomenon and the Earth's tilt is ~23.45 degrees now. The tilt varies cyclically between 24.5 degrees and 21.5 degrees with the latter number being more conducive to an ice advance and we are on the downswing of that cycle, i.e., we were at 24.5 a few thousand years ago and are heading for 21.5 degrees in maybe 3,000 years. If we are approaching the 21.5 number at the same time as the N Hemisphere is having it's summer while the Earth is at the furthest extreme in orbital eccentricity, then we have the makings of a new ice advance.
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cia
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Far away from here
Apr 1999
time: 05:32
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The problem I have with global warming is twofold. One, prove to me it isn't part of a natural cycle. Two, prove that it's actually happening at all. The temperature at ground level is different than atmospheric. So one can go up and the other down or vice versa. The scientists who say gloabl warming is occurring are liars and so are those who refute it. Truth is no one knows and no one I've seen so far can prove one way or the other. When a meteorologist cannot get tomorrow's weather right and some clown tells me the temperature trend for the next hundred years I laugh at them. There is no statistical, empiracle evidence of global warming or cooling and that's that. As an engineer I couldn't depend on anything they say for any data at all. Talk to me in 500 years when they have a clue.
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cia
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Far away from here
Apr 1999
time: 05:32
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Urban Ranger, I listened for three painful hours how a UN scientist told me how the surface temperature of the Earth is rising while the temperature planetwide at 10000 feet is falling and the oceans fluctuate too much to gain consistant reading. Look at the average CO and CO2 expulsions from a small volcanic explosion and measure it against the yearly output of the human activity the scientists peg on humans. It's a rat's pituitary gland of difference if the volcanio is not larger. It is in my mind human hubris that we can change the Earth's ecosystem at will. It's like saying enough pesticide can kill all the cockroaches in any major city. I would bet you a million to one against it.
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Ned
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of Aptos, CA
Oct 1999
time: 21:32
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quote:
Originally posted by cia
Urban Ranger, I listened for three painful hours how a UN scientist told me how the surface temperature of the Earth is rising while the temperature planetwide at 10000 feet is falling and the oceans fluctuate too much to gain consistant reading. Look at the average CO and CO2 expulsions from a small volcanic explosion and measure it against the yearly output of the human activity the scientists peg on humans. It's a rat's pituitary gland of difference if the volcanio is not larger. It is in my mind human hubris that we can change the Earth's ecosystem at will. It's like saying enough pesticide can kill all the cockroaches in any major city. I would bet you a million to one against it. |
Then, if you are right cia, we can do nothing to prevent a new ice age which is now "overdue."
Actually, if CO2 did rise enough so that it was noticed in the ice samples, I suspect it did have a small effect on temperature. Perhaps the differences between an ice age and not is very precariously balanced because ice ages tend to last 95,000 out of every 100,000 years. After a warm period is 5,000 years old, it may not take much to throw the Earth back into the cold.
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Az
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MACEDONIA - It's the name of the sovereign country to the north of Greece
Apr 2000
time: 07:32
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CO2 levels have NEVER been so high, AFAIK.
CO2 is a greenhouse gas.
take those two together and you get rapid global warming.
My biggest beef with this is that we're not controlling the process. There is no genuine, uninfluenced debate, since the side that is claiming there's nothing to worry about ( a fair pov ) is supported by interest groups which don't care at all about an honest debate on the subject, but do care a lot about their profits that would suffer because of any "unwelcome" conclusion from this debate.
In short: I'd believe anti-global warming people a lot more, if they weren't supported by certain corporations.
All that said, That "humans must be humble" bullshit from some eco-fans pisses me off just as much. We ARE able to control nature. We have been doing this for some time now. Now the trick is to control nature, while at the same time being fully aware of the consequences of our actions. More careful, more well-thought, ever self-improving? for sure. Raising our hands, and saying "we just aren't good enough"- No way.
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MrWhereItsAt
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New Year's Resolution: 2005 is the year of Where It's At - come get some.
Nov 2001
time: 17:32
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There's some severe scaremongering going on here.
Ice-core records from Greenland have shown that CO2 levels have risen and fallen to levels far beyond our current state, and at similar rates, over the last several hundred thousand years, at times without ANY human industry.
Satellite measurements have shown a global temperature increase of .00001% over the last 50 years, far less than some sources have used in their conclusions.
The estimated amounts of carbon dioxide ejected into the atmosphere from natural processes (fires and decomposure of vegetable material) still exceed human created CO2 by a large amount.
All these are examples of why we cannot simply assume we are having a large adverse effect on greenhouse gases.
Why not simply assume that we are responsible for the sharp decrease in magnetic field strength associated with the last 4-500 years of civilisation? After all, we have been creating magnetic fields of our own since around then. Just because two events are coincident does not mean they are connected. From geological, paleontological and climactic records it is clear the Earth goes through periodic changes from the current situation. Humanity may be having such a tiny influence on the presence of greenhouse gases as to be effectively NEGLIGIBLE.
My point is that, although we certainly create greenhouse gases, there is not sufficient evidence to indicate we have caused any change in temperature across the world that is dramatically influencing a regular cycle dictated by the sun and biological cycles.
Although climactic records as I have referred to come solely from Greenland, there is no greater reason to believe any of the evidence FOR the human-induced increase in greenhouse gases over that evidence that acts AGAINST such a conclusion. There is such uncertainty about this in scientific circles that you really have to take EVERY conclusion so far as being unproven. Do yourselves a favour and do not trust anyone in this matter without checking the results for yourself. I personally was convinced of humanity's cause of global warming until a lecture given recently by an atmosphertic physicist at my University. The reason for my belief was that I thought it was common knowledge that global warming was real. The evidence pointed elsewhere, and I adjusted my understanding accordingly.
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11-12-2003 13:24
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