By comparing today’s Nature paper to earlier versions I found just a few months old, it looks like some blame revisionism occurred after early discussions of this paper at NOAA in May 2012.
Over at Australian Climate Madness, Simon points out the coverage of the ABC for this new paper in Nature. He writes:
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Just as we must get rid of the Medieval Warm Period, the inconvenient Roman Warm Period must also be dealt with, and here’s a novel way of doing it: claim that it was man-made. In a single stroke, the RWP is scrubbed from the list of “natural warmings” that the planet has experienced in recent history, helping the Cause by demonstrating that it too was anthropogenic. The ABC reports:
A period covering the heyday of both the Roman Empire and China’s Han dynasty saw a big rise in greenhouse gases, according to a new study.
The finding challenges the view that human-made climate change only began around 1800.
A record of the atmosphere trapped in Greenland’s ice found the level of heat-trapping methane rose about 2000 years ago and stayed at that higher level for about two centuries.
Methane was probably released during deforestation to clear land for farming and from the use of charcoal as fuel, for instance to smelt metal to make weapons, says lead author Celia Sapart of Utrecht University in the Netherlands.
“Per capita they were already emitting quite a lot in the Roman Empire and Han Dynasty,” she says of the findings by an international team of scientists published today in the journal Nature (link to abstract). (source)
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Only one problem. Versions of this paper and slide presentation by the lead author in mid May 2012 make no mention of the Romans or Han dynasty whatsoever. Here’s the original abstract compared to the current one:
ORIGINAL – May 15th, 2012 at NOAA’s ESRL: (Source: http://www.esrl.noaa.gov/gmd/annualconference/abs.php?refnum=110-120409-A)
Isotope Variations in Atmospheric Methane Over the Last Two Millenia
T. Röckmann1, C. Sapart1, G. Monteil1, M. Prokopiou1, R.V.D. Wal1, P. Sperlich2, J. Kaplan3, K. Krumhardt3, C.V.D. Veen1, S. Houweling1, M. Krol1, T. Blunier2, T. Sowers4 and P. Martinerie5
1Institute for Marine and Atmospheric Research, Utrech University, Utrecht, Netherlands; 303-497-4988, E-mail: t.roeckmann@uu.nl
2Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, København DK-2100, Denmark
3Ecole Polytechnique Federale de Lausanne, Route Cantonale, Switzerland
4Earth and Environmental Systems Institute, Geosciences, Penn State University, University Park, PA 16802
5Laboratoire de Glaciologie et Géophysique de lEnvironement, University of Grenoble, Grenoble, France
Methane (CH4) is an important greenhouse gas that is emitted from multiple natural and anthropogenic sources. Atmospheric levels of CH4 have varied on various timescales in the past, but in many cases the causes of these variations are not understood. Analysis of the isotopic composition of CH4 preserved in ice cores provides evidence for the environmental drivers of variations in CH4 mixing ratios, because different sources and sinks affect the isotopic composition of CH4 uniquely. We have analyzed (δ13C) of CH4 in air trapped in Greenland ice cores over the last 2 millennia and find that the carbon isotopic composition underwent pronounced centennial-scale variations between 200 BC and 1600 AD without clear corresponding changes in CH4 mixing ratios. The long-term CH4 increase observed over this period is accompanied by a small overall δ13C decrease. Two-box model calculations suggest that the long-term CH4 increase can only be explained by an increase in emissions from biogenic sources. The centennial-scale variations in isotope ratios must be primarily due to changes in biomass burning, which are correlated with both natural climate variability including the Medieval Climate Anomaly, and with changes in human population, land-use and important events in history.
Now compare that original abstract presented to NOAA to the abstract of the paper in Nature being touted by the press on October 3-4, 2012:
Natural and anthropogenic variations in methane sources during the past two millennia
C. J. Sapart, G. Monteil, M. Prokopiou, R. S. W. van de Wal, J. O. Kaplan, P. Sperlich, K. M. Krumhardt, C. van der Veen, S. Houweling, M. C. Krol, T. Blunier, T. Sowers, P. Martinerie, E. Witrant, D. Dahl-Jensen & T. Röckmann
Nature 490, 85–88 (04 October 2012) doi:10.1038/nature11461
Methane is an important greenhouse gas that is emitted from multiple natural and anthropogenic sources. Atmospheric methane concentrations have varied on a number of timescales in the past, but what has caused these variations is not always well understood1, 2, 3, 4, 5, 6, 7, 8. The different sources and sinks of methane have specific isotopic signatures, and the isotopic composition of methane can therefore help to identify the environmental drivers of variations in atmospheric methane concentrations9. Here we present high-resolution carbon isotope data (δ13C content) for methane from two ice cores from Greenland for the past two millennia. We find that the δ13C content underwent pronounced centennial-scale variations between 100 bc and ad 1600. With the help of two-box model calculations, we show that the centennial-scale variations in isotope ratios can be attributed to changes in pyrogenic and biogenic sources. We find correlations between these source changes and both natural climate variability—such as the Medieval Climate Anomaly and the Little Ice Age—and changes in human population and land use, such as the decline of the Roman empire and the Han dynasty, and the population expansion during the medieval period.
Note that the two abstracts start out identically (highlighted in blue), and have similar language throughout presenting the isotope data, but that the Nature abstract has that added part about Roman empire and the Han dynasty.
In this slideshow presentation of the paper, http://www.esrl.noaa.gov/gmd/annualconference/slides/110-120409-A.pdf this graph from page 5 is quite telling:
As Simon points out on his blog:
The population, as the article goes on to say, was about 300 million, barely 4% of what it it today, and without any industrialisation apart from burning charcoal. I will leave it to you to consider the likelihood of such a tiny agrarian population having a significant effect on the climate.
The ABC’s coverage is similarly disingenuous. I’m not going to pay thirty bucks for the full article in Nature (if anyone has access, I would be grateful for a PDF), but eyeballing the tiny graphics published with the abstract (see above) seems to indicate that centennial scale changes in CH4 mixing ratio in the Roman period were in the order of a 20-40 parts per billion (that’s billion with a b). How the ABC can call this a “big rise in greenhouse gases” is unfortunately yet more evidence of agenda-driven journalism. It’s a tiny fraction compared with the industrial rise in CH4, which took mixing ratios to over 1800 ppb, yet the paper claims it is responsible for the significant warming that occurred around the time of the Roman empire?
The graph of CH4 compared to land use change seems like a good case of correlation:
But as we so often learn, when it comes to correlation, that does not always imply causation. Check out this multipanel graph from page 11 of the slide show:
Note graph “f” in red, which are temperature reconstructions from Moberg et al., 2005, Ljungquist et al., 2011, and try to find a correlation with Ch4 emissions in graph “b”.
From my view, there certainly doesn’t seem to be one that holds past 1000AD, when temperature started going down, but world population and land use increased. Likewise, correlation with transformed charcoal in “c” is weak as well.
The conclusion page 13 from the presentation seem pretty wishy-washy, especially the last point, where no specific blame is placed:
Conclusions
•Pronounced centennial-scale δ13C(CH4 ) variability in pre- industrial period
•Highly likely caused by changes in pyrogenic sources
•Correlation with NH charcoal index and anthropogenic land use rate of change
•Long term CH4 rise due to biogenic sources, and correlates well with land use data
•Both natural variability and anthropogenic activities may have influenced the CH4 budget in the pre-industrial period
The claim about the Romans and Han Dynasty seems quite a stretch when you actually look at the data/graphs. But as you can see in the ABC article, they don’t dare show you those things lest you draw conclusions of your own that don’t fit their narrative.
This might help you understand the motivation to start blaming the Romans and the Asians:
Atmospheric Physics and Chemistry Group
Dr Celia Julia Sapart
Master in “Climate Change”, University of East Anglia, Norwich (UEA), UK, 2006-2007
http://www.projects.science.uu.nl/atmosphereclimate/celia.php
Perhaps she got “Jonesed” into adding the part about the Romans and Han dynasty?
So if the Romans and the Chinese, with less than 1/10 of the current human population, and NO industrial revolution, managed to warm up the entire planet to a degree even higher than the MWP, which was even higher than we are now (STILL waiting for your answer to my question, tomT), then how, exactly, did the planet get so Freaking cold in between each of these three warm periods?
Or are they trying to claim that we should have fallen into a new period of glaciation, over 2000 years ago?
So during warm periods, humanity tends to produce expansionist civilisations who can draw off a lot of resource to support their huge bureaucracy (in relative terms), and when it gets colder and there is less resource to go round, these large empires fail. And it appears during these warm periods we have more methane produced – so?
Another case of correlation being taken as causation again I suspect, perhaps helped by the fact the authors may be following the CAGW line that there were no notable warm periods…
I was always of the opinion that at “O” AD they were actually too busy cutting down trees, trying to find some child in manger who threatened their very existence and practising at making crosses for one reason or the other. The only people feeling the heat was Herod and his mob. I could be wrong.
“Sexed up” data get new meaning now. When will this madness end?
Well, that leaves us with the Minoan Warming. I’m sure our Green Betters will think of something to explain that very big hump on the graph. There were certainly lots of tall jars and fragments thereof, lying around Knossos and Phaistos in the early seventies when I was there.
Maybe Big Pottery screwed the planet back in 1400 BC? I mean, they made some serious pots, those Cretans. It should be a warning to us all.
I don’t think it is implausible to think that there was some industrialisation and (quite significant) pollution in the heyday of the Roman Empire. I’ve seen quite a bit if interest in this among historians of the ancient world. This does not, however, explain the Roman Warm Period, which seems to have been warmer than the Mediaeval Warm Period, nor why it came to its end. In any event, the impact of the Romans on climate, given we’re talking about maybe c50m population in the whole Roman Empire and trivial population numbers in the rest of Europe, cannot have been significant.
I have to guess the ‘moderation required’ filters are set pretty high, as my first comment does not contain a single word that I would consider outre…..
never mind….
It was all that fighting and marching around all over the place..
Everyone KNOWS that humans put out more CO2 when they are doing that sort of stuff !!
Wasn’t there also a net decline in the Roman population in the 3rd & 4th centuries due to several visits from various plagues? This is cited by several historians as a major contributor to the downfall of the Roman empire. The population decreased enough that the Romans were unable to field armies as large as the barbarians that eventually forced their way into the Empire and eventually took it apart. In the 1st Century it was not uncommon for the Romans to field armies of 200,000, by the 3rd & 4th century they rarely fielded armies larger than 30,000, the average was around 15000. The Roman Legion itself decreased in total strength from around 5000 to less than 1500 and many of the ‘legions’ in the 4th Century were paper, they had no more than a hundred ‘skeleton’ staff.
Did the paper suggest any industrial mechanism that would account for the increased methane?
This is good. As Simon pointed out on the blog link, tiny population burning a bit of charcoal and cutting a few trees at the time. Now, in warnist style, embrace the fact that such activities caused the Roman warm Period for a minute.
Fast forward to today and we’ve had about the same effect with all of our emissions. So, clearly, a small human influence can cause the warming we’ve experienced but all the extra emissions today have had virtually no extra effect.
Logically, then,that all-important climate sensitivity must be so non-linear that it shrinks to virtually zero beyond some point. We’ve already passed that point because it was around the emission levels that the Romans achieved, so let’s get back to business as usual.
Hasn’t any noticed the Roman fondness for large scale contruction projects often made using concrete and covered with stucco, a type of plaster. Making both requires large amounts of lime and making lime, calcium carbonate, creates carbon dioxide!
posted this on an earlier thread. it’s a link i found on tom nelson’s website:
Atmospheric Physics and Chemistry Group
Dr Celia Julia Sapart
Master in “Climate Change”, University of East Anglia, Norwich (UEA), UK, 2006-2007
http://www.projects.science.uu.nl/atmosphereclimate/celia.php
Actually, it was all those cavemen striking flints with RECKLESS irresponsibility and COMPLETE DISREGARD for the planet that started this whole anthropogenic global warming thingy. I mean, it’s a well known Scientific Consensus Fact (TM) that rubbing two flintstones together produces excess heat that would not naturally exist and will, over time, and with sufficient repetition, raise the temperature of the whole world FOREVER!!!! There was a documentary about it on TV recently, and there’s that professor chappie in California who’s done a study and there was an article in a newspaper I read that PROVED IT so anyone who doesn’t believe this IRREFUTABLE evidence that we humans have been causing CATASTROPHIC climate change since we came down from the trees where we should go back to is an evil Gaia-hating d****r!!!! And furthermore (contd. on page 94)…
I see they’re also using the Team-approved “Medieval Climate Anomaly”, just to emphasise that this period was just odd and thus shouldn’t be considered.
Now, how is the Minoan Warm Period going to be dealt with?
It’s interesting to see that the Roman empire was rigidly defined by its relatively cheap walls, but China advanced up to 1000 miles beyond its hugely expensive walls.
This illustrates the great thing about ‘climate science’ and how you can make it up as you go along. However, there are a number of rules:
1. The purpose of the ‘research’ is refunding, nothing else really matters.
2. Conclusions need to be supported by the facts.
3. Facts are data that are routinely required to be manipulated/tortured/distorted/cherry picked to support the conclusions.
4. Models derived from the facts, as defined above, shall always take precedence over actual observations in the real world.
5. Scary is good. Exaggeration is good. Refusal to disclose raw data is good.
6. Data updates must always make previous conclusions appear understatements of alarming trends.
7. Government is there to be milked, so milk it. Expenditure on health and defense is a lower priority than ‘climate science’.
What about the Minoan Warm Period then? Or the Holocene optimum?
It’s funny that these appear to occur on a roughly 900 year cycle. Makes you think they are natural phenomena.
Here’s my take on what’s happened. Warm periods occurred naturally and led to a flourishing of human civilisation. All this economic activity such as forest clearing led to higher methane levels.
Once more they have mistaken cause for effect.
It’s worse than we thought! They don’t just want to take us back to 1800’s living, they want to take us back to the stone age (pre-bronze age).
The historical record is very clear about that. As many others have said: If you think global warming is scary, consider the effects of global cooling, the main one being famine.
Their own temp graphs show a 0.8 ish swing from MWP to LIA. Which is roughly what we’ve had from the instrumental record. So we can’t be beyond the realm of natural variability yet.
Hoist by their own petard.
So I wonder who the psychobabbler was that asked for this narrative to be added?
Just checked the change in the list of contrbutors to the second paper, D, Dahl-Jensen pops up. Guess what her interest is?
http://m.youtube.com/#/watch?v=I3totkLx_Ek&desktop_uri=%2Fwatch%3Fv%3DI3totkLx_Ek
Bill, the Roman Empire was afflicted with several plagues during the Imperial period post Augustus. The worst was probably the plague brought back from Persia by Trajan’s legions about 107 AD. I believe it’s now understood to be the Red Measles. Despite that, the population of the Empire grew steadily from the time of Augustus to at least the end of Diocletian’s reign in 300 AD. Throughout this period there was a steady expansion of transport infrastructure, roads, shipping and harbours, providing for better transport of food. You should remember that the principal limitation on the size of cities was availability of water, and the Romans were the only pre-industrial western civilization to make very large efforts to build water transport systems (aqueducts).
Now as to the army, don’t be misled by legion size. The army of Augustus consisted of 26 legions. It had approximately an equivalent force of mercenary auxiliaries, making a total standing military strength of about 250,000 men. Diocletian’s military reforms shrank the size of the legions but increased greatly the number of them. By his time, the Roman army’s principle weapon had become heavy cavalry styled after the Parthians, as Rome’s principal military threat was the Parthian Kingdom. The total manpower under arms, adding the frontier defence forces and the mobile armies well exceeded 350,000. And this was even after the enormous devastation of the Gothic invasions ca. 250 AD.
The failure of the army in the 5th century was not one of lack of numbers. The Roman army was capable of fielding very large armies in one spot, i.e. Julian’s invasion of Persia and the defeat of Atilla the Hun at Chalons. The problem was the steady depopulation of the rural countryside of free hold farmers (the source of military recruits) and their replacement by slave-operated latifundia. As a result, the Roman army by the 5th century was largely filled with barbarian mercenaries and even barbarian army commanders (Stilicho for example). Combining reliance on mercenaries with increasing disintegration of the governing structures led to a very rapid disintegration of the Empire in the west.
Diocletian tried to address the problem with his laws on binding occupations, but failed to deal with the underlying economics that were wiping out the independent free peasantry. As a result, all he did in the long run was create the legal basis for the feudal and manorial system.
In fact the population of the Empire would continue to rise despite the increasing political chaos in the Empire until the 6th century. Several factors contributed to this final collapse. Justinian’s reconquest of the western empire was accompanied by near total destruction of the agricultural and water infrastructure. Cities collapsed because the aqueducts were ruined and the new barbarian overlords had no capacity to repair them. The city of Rome’s population was still over 1 million at the turn of the 6th century. By the end of the 6th it was less than half that, mostly because of the destruction of the aqueducts. The military disintegration of the Empire in the wake of Alaric resulted in piracy exploding over most of the Mediterranean, resulting in severe limitations on grain supply from Africa, Sicily, Egpyt, Crimea.
The decline of the Roman Empire had many causes, some long term. But the most severe factors were the institutional and military disasters in the late 4th and 5th centuries.
Here is some historical perspective on Methane and CO2 levels over time.
Methane started increasing about 2000 BC (but it was higher in the Holocene Optimum at 8000 BC than it was during the Roman Period or when the industrial revolution started in 1750 AD).
http://s19.postimage.org/yg8o0ydub/Methane_12_K.png
So, blame the early farmers in the Fertile Crescent then rather than the Romans etc. And how much forcing exactly does that 75 ppb to 100 ppb rise in Methane from 2000 BC to 1750 AD equate to. Just 0.06 W/m2 according to the IPCC numbers or less than one-third of the change we experience in a single solar cycle. So I call garbage on the proposition in this paper. There is no climate impact from a 0.06 W/m2 change.
How about CO2 over the last 12,000 years. It started increasing around 5000 BC, well before any civilization was doing anything. This rise is more like 0.35 W/m2 so is 5 times as much as the Methane change.
http://img225.imageshack.us/img225/7021/co210kbc.png
And for some additional perspective, let’s look at Methane over the last 800,000 years. It falls during glacial periods and rises during interglacials so the Holocene Methane changes are well within the natural changes expected within an interglacial (also note there was no Methane Hydrate run-away when the Arctic got to +4.5C in the last Eemian interglacial for example, and it was actually higher in less-warm interglacials than the Eemian.)
http://img542.imageshack.us/img542/189/methane800k.png
Very poor study that leaves out all the important historical perspective.