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Greenhouse-gas levels highest for 650,000 years
news@nature.com ^ | 24 November 2005 | Michael Hopkin

Posted on 11/25/2005 10:41:45 PM PST by neverdem

Climate record highlights extent of man-made change.

Current levels of greenhouse gases in the atmosphere are higher than at any time in the past 650,000 years, say researchers who have finished cataloguing air bubbles trapped for millennia inside Antarctic ice. The record, which extends back over the past eight ice ages, shows that today's concentrations of carbon dioxide and methane far outstrip those in the past.

Atmospheric carbon dioxide levels have risen 200 times faster over the past 50 years than at any other time during this period, says Thomas Stocker of the University of Bern, Switzerland, who led the analysis.

The researchers studied air bubbles preserved in ice drilled from the Antarctic ice sheet as part of the European Project for Ice Coring in Antarctica (EPICA). The ice core represents a logbook of the state of the world's climate (see 'Frozen time') and goes back 210,000 years further than previous records.

After searching ice spanning the period of 390,000-650,000 years before present, Stocker's team has discovered that carbon dioxide levels in the atmosphere did not exceed 290 parts per million during that time. Today, that figure is around 375 parts per million.

The situation is similar for methane: during this period, levels hovered around 600 parts per billion. Today's atmospheric methane concentration is well over 1,700. Stocker and his colleagues report the results in Science1,2.

Unprecedented push

The burning of fossil fuels in the industrial era has pushed greenhouse-gas levels far beyond their natural fluctuations, says Stocker. "This is really something unprecedented," he says. Humans, by releasing fossil fuels from their imprisonment underground, are now adding greenhouse gases to the atmosphere on top of those released as part of natural climate cycles.

The news comes as world leaders plan to attend a United Nations climate change conference in Montreal, Canada, which begins on 28 November. Delegates will discuss current efforts to reduce greenhouse emissions, and what plans should follow on from the initial phase of the Kyoto Protocol, which ends in 2012.

The past four ice ages and their intervening warm periods are thought not to have been typical. Glacial cycles before this had longer, cooler intervening periods than more recent ones. Researchers are unsure why this is, although they hope the ice cores may hold some clues.

Unnatural changes

The newly analysed ice does show that although the climate is in constant flux, it is capable of producing extended warm phases even when carbon dioxide levels are stable, says Stocker. Two places in the record, for example, are marked by periods of almost 30,000 years when temperature hardly changed at all. And the beginning of these 'interglacial' phases was not linked to rises in carbon dioxide.

That's not to say that current rises in temperature are due to natural shifts, as some climate-change sceptics have claimed. "The CO2 emitted now is not part of the natural cycle," Stocker points out.

"In the palaeorecord there's no human activity driving the change," says Chris Jones, of the Hadley Centre for Climate Prediction and Research in Exeter, UK. The current challenge facing climate modellers is to work out the one-way effect of the huge spike in greenhouse gases now being pumped into our skies by human activities.

References doi:10.1038/news051121-14 SiegenthalerU., et al. Science, 310. 1313 - 1317 (2005). SpahniR., et al. Science, 310. 1317 - 1321 (2005).


TOPICS: Business/Economy; Canada; Culture/Society; Extended News; News/Current Events; Technical; United Kingdom
KEYWORDS: greenhousegases; icecores
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To: neverdem
Current levels of greenhouse gases in the atmosphere are higher than at any time in the past 650,000 years... today's concentrations of carbon dioxide and methane far outstrip those in the past.

Faulty analysis since CO2 and Methane are not the largest component of greenhouse gases and are in fact only a tiny fraction. The main greenhouse gas cannot be measured in ice cores where its concentration will vary with the temperature of the ice and it is perfectly natural:

"Water Vapor is the most abundant greenhouse gas in the atmosphere, which is why it is addressed here first. However, changes in its conentration is also considered to be a result of climate feedbacks related to the warming of the atmosphere rather than a direct result of industrialization. The feedback loop in which water is involved is critically important to projecting future climate change, but as yet is still fairly poorly measured and understood.

As the temperature of the atmosphere rises, more water is evaporated from ground storage (rivers, oceans, reservoirs, soil). Because the air is warmer, the relative humidity can be higher (in essence, the air is able to 'hold' more water when its warmer), leading to more water vapor in the atmosphere. As a greenhouse gas, the higher concentration of water vapor is then able to absorb more thermal IR energy radiated from the Earth, thus further warming the atmosphere. The warmer atmosphere can then hold more water vapor and so on and so on. This is referred to as a 'positive feedback loop'. However, huge scientific uncertainty exists in defining the extent and importance of this feedback loop. As water vapor increases in the atmosphere, more of it will eventually also condense into clouds, which are more able to reflect incoming solar radiation (thus allowing less energy to reach the Earth's surface and heat it up). The future monitoring of atmospheric processes involving water vapor will be critical to fully understand the feedbacks in the climate system leading to global climate change. As yet, though the basics of the hydrological cycle are fairly well understood, we have very little comprehension of the complexity of the feedback loops. Also, while we have good atmospheric measurements of other key greenhouse gases such as carbon dioxide and methane, we have poor measurements of global water vapor, so it is not certain by how much atmospheric concentrations have risen in recent decades or centuries, though satellite measurements, combined with balloon data and some in-situ ground measurements indicate generally positive trends in global water vapor." National Oceanic and Atmospheric Administration - Greenhouse Gases

methane: during this period, levels hovered around 600 parts per billion. Today's atmospheric methane concentration is well over 1,700.

This is only a half-truth that lets one infer that methane is rising. In fact it appears to have reached a new equilibrium:

"Methane is an extrememly effective absorber of radiation, though its atmospheric concentration is less than CO2 and its lifetime in the atmosphere is brief (10-12 years)... Direct atmospheric measurement of atmospheric methane has been possible since the late 1970s and its conentration rose from 1.52 ppmv in 1978 by around 1%/year to 1990, since when there has been little sustained increase. The current atmospheric concentration is ~1.77 ppmv, and there is no scientific consensus on why methane has not risen much since around 1990." Ibid.

the initial phase of the Kyoto Protocol, which ends in 2012.

The end of the Mayan calendar! Coincidence?! ;-)
41 posted on 11/26/2005 10:45:36 AM PST by UnbelievingScumOnTheOtherSide (Give Them Liberty Or Give Them Death! - IT'S ISLAM, STUPID! - Islam Delenda Est! - Rumble thee forth)
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To: mountn man
"A few good volcanoes can make our input look minuscule."

don't you mean OUTPUT? That orrifice was not made for input.


Input and output are strictly a point of view. From the atmosphere's POV both are inputs.
42 posted on 11/26/2005 10:50:05 AM PST by UnbelievingScumOnTheOtherSide (Give Them Liberty Or Give Them Death! - IT'S ISLAM, STUPID! - Islam Delenda Est! - Rumble thee forth)
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To: mountn man
No, I was referring to what we contribute to the atm. Therefore, input was grammatically correct.
43 posted on 11/26/2005 11:36:07 AM PST by aliquando (A Scout is T, L, H, F, C, K, O, C, T, B, C, and R.)
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To: aliquando

Only that agriculture is the weakest link in the chain of civilization, and it wouldn't take changes large enough to flood NYC to cause fairly drastic shifts in growing seasons.

Agriculture made civilization possible. It's failure would make civilization impossible.


44 posted on 11/26/2005 12:18:34 PM PST by UncleJeff
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To: Matchett-PI
You embarrass yourself.

You have your beliefs and I have mine. Yes I am a young-Earth creationist.

45 posted on 11/26/2005 4:43:01 PM PST by amigatec (There are no significant bugs in our software... Maybe you're not using it properly.- Bill Gates)
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To: UnbelievingScumOnTheOtherSide

Thanks!


46 posted on 11/26/2005 5:30:51 PM PST by phantomworker (We don't see things as they are, we see things as WE are.<==> Perception is everything.)
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To: phantomworker
What's your take? Just curious.

Doesn't seem like anything all that new though its interesting that they note previous warming periods were not the result of increased C02 levels. I happen to think reflective particulate matter contributes more than carbon dioxide and that CO2 is a fairly good indicator of that. I don't necessarily think we are the only culprit of global warming but I do think we should be mindful of the potential impacts of our actions (precautionary principal).

The real thing that bothers me regarding global warming are the extremes- the people in complete denial and the alarmists. The truth probably lies somewhere in the middle and it is in our best interest to curb these trends. The problem is that air quality is a true tradgedy of the commons- those that do the damage are not the only people who will be affected. That leaves plenty of room for exploitation. IMO

47 posted on 11/28/2005 6:38:10 AM PST by GreenFreeper (Not blind opposition to progress, but opposition to blind progress)
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