Want to make a paper more alarming and appealing to coverage? Blame the Romans for climate change

English: Locator map for the Roman Empire and ...
English: Locator map for the Roman Empire and the Chinese Han dynasty, c. AD 1. (Partially based on Atlas of World History (2007) – World 250 BC – 1 AD) (Photo credit: Wikipedia)

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:


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)


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:

δ13C measurements on air trapped in Greenland ice cores from NEEM (black diamonds; this study), EUROCORE (blue diamonds; this study), GISPII23 (green diamonds) and Antarctic ice cores from Law Dome1 (red diamonds) and the WAIS divide

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:


•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


Perhaps she got “Jonesed” into adding the part about the Romans and Han dynasty?

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October 4, 2012 12:54 am

Whole thing is a bit of a joke.
Natural causes and natural causes.
There is a relatively good instrumental record for the CET 1650-1750:
The sharp drop from 1650 to 1690 was followed by even steeper rise 1700-1740, neither can be explained by any charcoal or even the ‘witches burning’, but there are perfectly plausible natural reasons.

Ian W
October 4, 2012 12:55 am

Is there not one inquiring journalist who would hold these ‘academics’ up for ridicule? Pointing out the discrepancies in what they have claimed and laugh at their claims? I realize that these people want tenure and more research funding – many of us have been there – but some of these claims would be cause to fail a first year undergraduate paper. I remember a similar claim that neolithic camp fires had caused the rise in temperature at the beginning of the Holocene. This type of paper does not merit serious discussion but should be seen as a source of humor; perhaps there ought to be some new competition for the most fatuous claims in a research paper?

Eyal Porat
October 4, 2012 12:58 am

At 0 AD the world human population was about 200 million.
It seems the Romans and Hans SUVs were some mo**erf***er big polluters!

October 4, 2012 1:09 am

Yes. Eyal Porat. You beat me to it. At 3% of curremt world polulation their per capita emissions would have to be 30 times higher. Without phone chargers to leave inadvertently!

October 4, 2012 1:12 am

Both abstracts have the flavor of stealth-and-run. “Here is the quandary….there MUST be an anthropogenic component”, seemingly disguised as an innocent summary of possible explanations for odd isotopic ratios. Result: that queasy feeling that someone is trying to smuggle the meme into the debate. But Wait! They don’t even smuggle in the second abstract…they just drive an armoured Semi full of weasel words straight through the checkpoint guardhouse!

October 4, 2012 1:14 am

An inquiring journalist? What an *intriguing* concept! Someone should try that.

October 4, 2012 1:14 am

I looked for the signature of the Black Death (around 1350), when a third of the world’s population, and half of Europe’s population died, and its well documented that large areas of farmland reverted to forest. Yet their pyrogenic CH4 ( from increased charcoal production) rises after 1350. Highly unlikely IMO. With the reduced population, metals and metal tools/weapons would have been in surplus, and smelting and smithing greatly reduced.

October 4, 2012 1:17 am

At least “climate scientists” cannot blame the British Empire for anything since it was spreading while we were emerging from the Little Ice Age!
Of course, if climate scientists could get rid of the Little Ice Age …

October 4, 2012 1:19 am

The madness deepens…

October 4, 2012 1:31 am

I think the Monty Python sketch about what the Romans have done for us is in need of a revision…
I blame it on that scene at the start of Gladiator – lots of carbon being produced by burning forests… a very none eco way to go about having battles..

October 4, 2012 1:36 am

We’re often told that we must reduce the global population and return to an agragrian paradise. But blimey, look what happened when the population was just 3% of what it is today and everyone was a farmer!

Old England
October 4, 2012 1:38 am

Population expansion occurred during warmer periods and population contraction occurred during cooler periods. Civilisations grew and developed more rapidly during the warmer periods and declined in the cooler.
Hardly surprising then that there was more human activity as civilisation leaped forwards in the warmer, more benign periods and less activity in the cooler periods when life was harsh and difficult.
This is no different to Gore’s false claims that CO2 rises preceded rather than followed temperature rise.
I wonder what the payment – sorry ‘grant’ – was for producing this nonsense.

October 4, 2012 1:41 am

Next: how to get rid of the Holocene Climatic Optimum (9,000 – 5,000 BP).
Onward and upward, comrades …

October 4, 2012 1:42 am

to quote Python from Life of Brian:
”and what have the Romans ever done for us?’…………

October 4, 2012 1:47 am

Infamy, infamy, they’ve all got it infamy…
Well some climate scientists belong in their very own ‘Carry On’ film!

Alan the Brit
October 4, 2012 1:50 am

Well at least we poor old Brits can stop worrying about being blamed for it all now, it’s the Romans, “what have they ever done for us?”, given us global warming it seems, on top of all the other ubiquitous stuff we often take for granted today, the aqueduct, the viaduct, roads, civil engineering, military engineering, law & order, irrigation, sanitation, education, hosptials, public health, public baths, art, Latin, central heating!

Bloke down the pub
October 4, 2012 1:50 am

There are some tarts who give whores a bad name. Anything for the filthy lucre.

Chad Wozniak
October 4, 2012 2:09 am

Ian W
More bull@#$%&*!! from the CAGW reactionaries. And the media’s blind acceptance of it is so heinous as to defy belief.
I’ve come to the conclusion that the mass media should be compelled by law, as a condition of their broadcast and publishing licenses, to report the truth along with their lies. There’s no problem of free speech, since they can go right along with their lying, but there is no reason why they should not be forced to also tell the other side of the story on AGW and any other such contentious issue. And they should be explicitly required to say that what they publish is their opinions, not necessarily facts, and that there are or may be views different from theirs.
If this sounds extreme – news reporting is a consumer product, and we require truth in packaging, truth in lending, and warning labels on hazardous products like cigarettes – why shouldn’t the news media be subject to the same standards as other businesses? They are capable of doing at least as much harm as the tobacco companies or crooked lenders. And it’s only a matter of honesty.
Of course the evil media empire will cry foul, but the real reason for that is that their tyrannical agenda and the lies they are telling would be promptly exposed for what they are, for all to see.
And I would apply the same strictures to the academic journals’ publishing licenses, and with respect to instruction in the universities – I would make accreditation conditional on their allowing and supporting all kinds of views on such issues as climate change.
Of course the academics will also squawk about this, but then they can be presumed to be like my former history professor colleague, who thought that the Soviet system was so much more efficient and humane than ours, 80 million murdered to the contrary notwithstanding – and said that was “a necessary step in reforming society.”
Given the CAGW crowd’s willingness to cause tens of millions of avoidable deaths through economic destruction, one would have to assume that those deaths are A-OK with them and a “necessary step in reforming society.” The next Holocaust, here we come! THAT’S the catastrophe we need to be on our guard for.

Berényi Péter
October 4, 2012 2:11 am

Heh, it’s easy. One don’t even need to deny the Medieval Climate Optimum any more, if only the Chinese industrial revolution of the Song Dynasty (宋朝; 960–1279 CE) could be blamed for it.
The per capita iron output rose sixfold between 806 and 1078, and by 1078 Song China was producing 127,000 t in weight of iron per year
They’ve even invented coke to prevent catastrophic deforestation, which was well under way by the end of this period due to charcoal overuse.

cui bono
October 4, 2012 2:11 am

Now add climate change to the list…

October 4, 2012 2:15 am

If the abstracts diverge,with a period of almost six months between,then you really will need to check the full paper.

Steve C
October 4, 2012 2:25 am

I had to read this twice and check it wasn’t April 1st, but yes, they really do seem to be claiming that. I guess a lot of the problem must have been all those 4 horsepower chariots in the Roman Games (vide ‘Ben Hur’) – horses fart just like cattle do, after all. Unbelievable, literally.
Plus, if they’re going to be consistent about this, then their next target must be to explain away the Minoan warm period, which was even warmer than the Roman. The entertainment value should increase yet further.

John Marshall
October 4, 2012 2:29 am

There is no consideration of solar radiation changes that will produce 13C from 12C and these data will not be available without much more research.
The whole paper relies on the iffy GHG theory. Other theories are available.

October 4, 2012 2:30 am

Is Celia Sapart any relation to Deirdre Spart of Private Eye fame ?

October 4, 2012 2:34 am

I remember many years ago being taught not to jump to conclusions about correlations between various variables. An example given to us, which I have always remembered, was that someone had observed that over a particular period an increase in the birth rate in Germany had occurred at the same time as an increase in the Stork population. And I am still convinced to this day that Storks do bring babies into this world because I saw the “facts” for myself! It appears Dr Sapart didn’t have the opportunity for a rigorous education I was fortunate enough to have.

October 4, 2012 2:45 am

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?

October 4, 2012 2:45 am

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…

October 4, 2012 2:48 am

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.

October 4, 2012 2:52 am

“Sexed up” data get new meaning now. When will this madness end?

October 4, 2012 3:02 am

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.

October 4, 2012 3:12 am

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.

October 4, 2012 3:21 am

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…..

October 4, 2012 3:21 am

never mind….

October 4, 2012 3:23 am

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 !!

Bill Marsh
October 4, 2012 3:26 am

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?

October 4, 2012 3:32 am

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.

dangerous sheep
October 4, 2012 3:56 am

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!

October 4, 2012 4:09 am

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

October 4, 2012 4:18 am

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)…

Adam Gallon
October 4, 2012 4:20 am

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?

October 4, 2012 4:31 am

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.

Peter Miller
October 4, 2012 4:36 am

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’.

Vince Causey
October 4, 2012 4:39 am

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.

John West
October 4, 2012 4:42 am

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).

October 4, 2012 4:54 am

Old England says:
October 4, 2012 at 1:38 am
Population expansion occurred during warmer periods and population contraction occurred during cooler periods. Civilisations grew and developed more rapidly during the warmer periods and declined in the cooler.

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.

October 4, 2012 5:06 am

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.

October 4, 2012 5:08 am

So I wonder who the psychobabbler was that asked for this narrative to be added?

October 4, 2012 5:28 am

Just checked the change in the list of contrbutors to the second paper, D, Dahl-Jensen pops up. Guess what her interest is?

October 4, 2012 5:32 am

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.

Bill Illis
October 4, 2012 5:38 am

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).
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.
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.)
Very poor study that leaves out all the important historical perspective.

alex the skeptic
October 4, 2012 5:41 am

>>“Per capita they were already emitting quite a lot in the Roman Empire and Han Dynasty,” she says of the findings…..<<
Problem is that there was much less humans2000 years ago than there is today. There were about 250 million people in year zero, and 7,000 million today.
So, after having flattended out the MWP and the RWP, there's still the prvious one, the Minoan warm period. Was that anthropogenic too? An interesting read:
Isotopes of oxygen analyzed from deep ice cores drilled in Greenland’s massive two mile thick ice sheets show that today’s “record warmth” is not even close to how warm it’s been in the recent past. These oxygen isotopes can act as a proxy or substitute for temperature. What they reveal is that the earth was much warmer than today for most of the last 10,000 years by 1 to 4 degrees Fahrenheit. The entire warming of the last 160 years is just 1 degree Fahrenheit, half of which took place between 1910 and 1945 when humans could not have had any effect. In fact these ice cores reveal that earth’s temperature has been rising for 200 years, rebounding from a 500 year cold period known as the “Little Ice Age.” Further examination of the ice core temperatures show that earth’s temperature peaked some 3,300 years ago in the Minoan Warm Period and has been falling ever since.

October 4, 2012 5:42 am

Let me think this one through. Methane levels rose and remained at a high level for around 200 years. What anthropogenic activity caused this? Deforestation and the anaerobic production of charcoal?
But charcoal is burned, converting it to carbon dioxide and ash. Methane breaks down in the atmosphere into water and carbon dioxide. It has a half life of around 8 years. And deforestation reduces carbon sinks. Yet we are told elsewhere that ice cores show carbon dioxide levels were stable for thousands of years prior to the Industrial Revolution. This despite the assertion that natural sinks cannot cope with increases in anthropogenic carbon dioxide and it hangs around for hundreds of years. This explanation doesn’t add up.
And why did the Roman Warm Period ever end? Why did all these extra anthropogenic GHGs not prevent global cooling and a drift into the Dark Ages?
How about an alternative theory. The Roman Warm Period was caused by natural events probably resulting in a reduction in average cloud cover. This warming produced a thawing of the tundra and the release of methane from frozen ground in regions such as Greenland. This period ended with the Dark Ages which were caused by natural events probably resulting in an increase in average cloud cover. This cooling produced a freezing of the tundra and choked off the release of methane. No anthropogenic explanation is necessary.

October 4, 2012 6:01 am

Vukcevic’s witch burning theory is excellent!! You are all missing an important point. Adding this little bit of BS about the Hans and the Romans is probably what made it a Nature paper in the first place. I don’t blame the author (much) for playing the hand she was dealt.

Tim Clark
October 4, 2012 6:36 am

Eyeballing the graphs, a 20-40 ppb increase caused a .4C increase in temperature between 0 AD and 1000 AD. From then to now it has increased to 1800 ppb. Using my mystical “two-box model calculations”, the increase to 1800 ppb should have raised the temperature 10 degrees C. However, I haven’t included the positive feedback effect, so recalculation including those forcings in my mystical “two-box model calculations”, will surely show we are actually 45 degrees C warmer now. Hansen better add some more adjustments if he wants to support my model.

Pamela Gray
October 4, 2012 6:45 am

So I suppose you could say that the change in salmon and elk populations causes the PDO statistic to flip. Yes. I get the logic now. No wonder springtime in NE Oregon is getting colder. The bat population is changing. Damn bats.

October 4, 2012 6:56 am

I’m not even going to warrant this with a discussion over historic facts. I will simply dismiss this “study” as very expensive toilet paper.

Steve Jones
October 4, 2012 7:00 am

Yarmy says:
October 4, 2012 at 1:36 am
An excellent observation that means the cAGW crowd have painted themselves into a corner. Effectively, other than completely wiping out the human race, there is no solution to AGW if you follow their logic. We might as well take advantage of all that cheap energy that is available from fossil fuels anyway.

October 4, 2012 7:01 am

A minor edit is suggested:
“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 climate change junk science activists smoke too much crack.”

October 4, 2012 7:02 am

Let’s assume there is a causal correlation between the Roman Empire and a climatic “Roman Warm Period.”
Which is more likely?
That a horse drawn, sail and oar ship driven Roman Empire changed the earth climate from cool to warm, or
A natural variation in earth’s climate, a warm phase, created the Roman Empire with its bountiful harvests, water wheel driven grain and lumber mills and a need to build aquaducts to serve its growing cities?
There is a corrollary question? Was there a causal relationship between the fall of Roman Empire and Climate?

P Wilson
October 4, 2012 7:02 am

how would they whitewash the Holocene optimum, which was both longer in duration and warmer than either the MWP or the RWP, and saw the rise of civilisations?

October 4, 2012 7:05 am

Ok, I can’t resist.
The Romans managed to plant wine pretty far north (England) and in China culture and technology exploded. The MWP has its equivalent in Asia a well. Not only was wine being planted very far north in Europe (Denmark), in China and Japan culture exploded again, leading to the first novel of mankind. Which means, in both cases it was significantly warmer than today. Try planting wine today in Denmark or Northern England. it won’t really work, because it’s too cold.
Whoever wrote this study is trying to rewrite history. From my point of view as a Japanologist specialized in history these “scientists” are guilty of raping history and should be treated as such.

October 4, 2012 7:13 am

The Romans produced a lot of cement 2000 years ago (ref. “Roman Concrete”) and from what we can tell burned a lot of wood/charcoal to do it. Given cement production is 2nd to fossil fuel use on the CAGW hit list, I am surprised the paper didn’t make this link.

October 4, 2012 7:29 am

Next on the list…………The Holocene Climate Optimum. 😉 How these goons seem shocked that the tide is turning against them is beyond me.
It would be interesting to read about how the biosphere responded during the Roman Warm Period.
The Pacific Islanders were doomed during this time.

Half a world away in the tropical Pacific Ocean a similar saga unfolded. During the Greco-Roman climatic optimum, the Polynesians migrated across the Pacific from island to island, with the last outpost of Easter Island being settled around A.D. 400 (35).

October 4, 2012 7:35 am

[behind the scene at Clima-clown Crisis Management meeting]
Fellow Clima-clowns, we’ve been exposed and are now in a similar position as Governor William J Le Petomane in the movie Blazing Saddles….”We’ve gotta protect our phoney-baloney jobs, gentlemen, we must do something about this immediately”. We can’t make the warm bumps disappear from the hockey stick handle…..any suggestions ?
Well….i did find some extra Methane molecules hiding in some ice cores….can we blame CH4 on the Romans….how bout also blaming the Hans ? ? ?
GREAT….but Romans and Hans is not scarey enough….we gotta blame the INDUSTRIALIZATION of those evil empires. HEY….why not rebrand this as the IRON AGE AGW ! ! ! And while we’re at it, we can rename that pesky Minoan Warming the BRONZE AGE AGW ! ! !
FANTASTIC….get this info to one of the UEA shills and into the phoney-baloney media ASAP ! ! !

P Wilson
October 4, 2012 7:36 am

OK. if we fast forward to today: 75% of the current interglacial the holocene period has been warmer than the last 20 years. It tends to runb in centuries so the 17th century was cold, the 18th century warmer the 19th century cold, the 20th century warmer, etc.. The period used by the AGW protagonists starts around 1850 – which was the coldest period in the entire holocene., so naturally post this period anything is going to be naturally warmer

October 4, 2012 7:41 am

What I find interesting is that the lead author on the first paper is the last author on the second paper. Usually when the second paper (from the same research group) is based off the data/conclusions of the first paper, the lead author on the first paper is given second or at least third billing…

October 4, 2012 7:44 am

The Cheefio had a great post on C4 and C3 pathway plants produce different C12 and C13 amounts.
And then there is this:
“Just a few days ago, only the second isotope study of millet consumption in the Roman Empire was published, by Pollard and colleagues in the American Journal of Physical Anthropology. In a small Romano-British cemetery in Kent (late 3rd-early 4th century AD), a salvage archaeology project uncovered a dozen burials that were simple in nature: only coffin nails and hobnails from boots were found in most graves. Among these simple farmers, though, was an individual with a surprisingly high carbon isotope value, so Pollard and colleagues undertook a dietary (C/N) and migration (Sr/O) study of the individuals.
The anomalous partially complete skeleton was that of a male over the age of 45 buried wearing hobnail boots. The individual’s nitrogen isotope ratio was a bit high (11.2 permil), indicating aquatic resource consumption, but was not higher than average for Roman Britain. His carbon isotope ratio from collagen, however, came in at -15.2 permil, in stark comparison to the average of the other individuals of -19.8 permil (see below). This difference may not seem dramatic until you factor in the standard deviation – variation within the d13C ratios of the others from the site was only 0.3! This person was therefore eating a whole bunch of C4 resources – millet, sorghum, or animals foddered on those grains.”

October 4, 2012 7:44 am

Are there any straws left for the drowning man? Burning charcoal merely releases the CO2 captured during the hundred to three hundred years or so of the life of most trees.

Kim Moore
October 4, 2012 7:45 am

Use Google Images and search for the lead authorette and see a picture of her in a large important lab space standing in front of a large important piece of scientific equipment. She is dressed in burly work gear and about to embark on an important scientific bit of inquiry by probing into the secrets of the past in order to understand the present and future.
Youth is so exuberant.

October 4, 2012 7:47 am

Following hard on the heels of the Roman Warm Period and the Medieval Warm Period was the Little Ice Age. A time when the world’s population was even higher. Man’s extra co2 was unable to prevent natural cooling. Oh damn!

October 4, 2012 8:07 am

The three carbon isotope excursions shown are actually positive (more 13C) against an atmosphere that is strongly biased toward 12C, (13C -47% of the Pee Dee zero). These excursions are very subtle by geological standards and at this sensitivity could concievably reflect human influence.
The trouble is we have learned that the isotope signature of fossil fuel burning is NEGATIVE, and the burning of the Eurasian forests should produce a negative signature as well. Trees are future fossil fuels.
More interesting than the machinations of greenhouse theologians is how the atmosphere is able to maintain its negative “excursion” and why the biologically redjected 13C seems to wind up in the ocean.

October 4, 2012 8:13 am

Lefties are famous, practiced, and successful at changing the game when they are not pleased with the outcome. They get away with it because the so-called watchdogs of the media let them – due variously to corruption, laziness, and ignorance.

October 4, 2012 8:19 am

This just in: New study in Nature suggests that paleo-indians, using Clovis points to chip ice from glaciers for margaritas, helped end ice age.

cui bono
October 4, 2012 8:27 am

The Neolithic revolution was clearly a major mistake.
In fact, we can go further back for the source of our present-day ills. Our tendency to walk upright on two legs led to a superiority complex, a psychological perspective which separated us from the rest of Gaia’s species, allowing us to claim a right to exploit animals and all other resources for our own benefit.
There is only one solution – get back on your hands and knees people, and keep your eyes on the ground.
Copyright LooneyLewPress 2012 (publication pending as soon as I’ve bribed the editor).

Keith W.
October 4, 2012 8:34 am

Surprisingly, Seth Borenstein reports on a study showing scientific fraud increasing in several journals including PNAS and Nature articles.
This Roman Warm Period study masquerading as science is more similar to the transparent propaganda employed by the Nazi’s in the 1930’s to achieve their political aims in the Rheinland, Austria, and Czechoslovakia, Real science or history it is not.

October 4, 2012 8:40 am

Jimbo stole my primary comment: If you try to blame the RWP and the MWP on anthropogenic (sp?) sources then the cooler period in between them, and also the little ice-age, can only be explained through external forcing.
So my fall back comment is this… if just 300 million humans can cause the temperature to climb as much as it did during the RWP, then with 25 times as many humans today we should all be roasting – literally. Another elegant hypothesis ruined by virtue of conflicting with the evidence
PS Regarding the temperature vs land-under- cultivation graph. Has anyone considered that temperature influences land-under-cultivation, not the other way round?

October 4, 2012 8:40 am

Friends, Romans, countrymen, lend me your fears,
I come to bury science, not to praise it…..
What seems much more plausible is that major NATURAL warming periods (which seem to happen in approximately 1,000-year intervals: 1000BC/Minoan WP, 0AD/ROMAN WP, 1000AD/Medieval WP, 2000AD/Modern WP) enable substantial agricultural surpluses, which vastly increases economic growth/trade, leading to major advances in civilizations/empires during those historic WARMING PERIODS.
Such an hypothesis makes much more sense than attributing economic growth to causing anthropogenic GW during those warming periods.
CAGW IS starting to get even more ridiculous, pathetic and desperate.

Neil Jordan
October 4, 2012 8:58 am

The Roman and Chinese greenhouse gas emission article made it into this morning’s California Department of Water Resources news, plus two more articles in the same vein:
Study reveals ancient greenhouse gas emissions
An analysis of Greenland ice core samples indicates significant global methane emissions per capita during the Roman Empire and China’s Han Dynasty — much greater than had been known.
A forecast for the American West: hot and hotter
Climate change will mean more and larger fires in 11 Western states.
Climate-change denial getting harder to defend
But the skeptics keep shifting their arguments, so it is crucial to continue pursuing scientific data on the issue.

October 4, 2012 8:58 am

Ruddiman already fingered humanity for the Holocene Climatic Optimum:
It’s amazing how climate managed to change on Earth for its first 4.54 billion years without the help of man-made gases, yet somehow it went from being covered in oceans of molten rock to of water ice & every possible climate in between without benefit of agricultural or industrial revolutions.

October 4, 2012 9:00 am

I agree that the journalism is atrocious. The science simply says that it is possible by isotopic analysis to separate out anthropogenic methane from naturally generated methane, if we accept that the isotopes let us do an attribution of source. The science says nothing about Romans being significant actors in climate change – that is the journalist’s interpretation.
Poor journalism, but the science is straight ahead measurement. no models or proxies in sight. Nice hockey stick, though.

October 4, 2012 10:22 am

Put me down for one of those V8 chariots. 😉

October 4, 2012 10:35 am

These super scientists are not very good at orders of magnitude. You can relate CH4 to CO2 by the greenhouse potency. It is roughly 20 times more potent. So the 20-40 ppb of CH4 is equivalent to 400-800 ppb of CO2. For CO2 this is expressed more normally in parts per million. So the CH4 change is equivalent to less than 1 ppm change in CO2. Let us go for the top end, and take the UNIPCC’s assumption that a doubling of CO2 will cause 3 Celsius of warming. Also assume levels of CO2 of 280ppm, and you still get absolute tops 0.01 Celsius of warming.
These fellows need to stand back and do a bit of basic sense-checking of their results.

Kelvin Vaughan
October 4, 2012 11:04 am

All those galloping horses breathing out the dreaded CO2 no doubt and methane from the other end!.

October 4, 2012 11:24 am

Fom the GWPF
“The past 5,000 years of the GISP2 temperature history of the Greenland Ice Sheet, adapted from Drake (2012), who denoted the general locations of the Late Bronze Age (LBA), the Roman Warm Period (RWP) and the Medieval Warm Period (MWP) in their original work”

October 4, 2012 11:58 am

From 1500BC to 400BC Greenland was warmer than today!
World’s most northerly lake comes back to life
The lake formed about 3500 years ago when local precipitation increased, says Perren. A few species of silica-shelled algae called diatoms lived in the young lake, but their populations declined as regional temperatures cooled, and they vanished entirely 2400 years ago.
Sø, the world’s most northerly lake, was entombed beneath a near-permanent layer of ice some 2400 years ago. Now it is beginning to thaw.


Jeremy Thomas
October 4, 2012 1:39 pm

Next stop: we have to get rid of the Holocene Optimum…

stephen richards
October 4, 2012 2:08 pm

I am saddened. The morons are not appearing anymore to defend their god and Oblarny forgot his lines and Gore put his big boots into his even greater mouth. T’was the altitude what done it.

October 4, 2012 2:32 pm

Following on from mwhite’s comment : What is most interesting about this graph is that it suggests the late bronze age was significantly warmer than the Roman Warm period, which was significantly warmer than the Medieval Warm period.
It also suggests about 80% of the last 5,000 years were warmer than today, even though the CO2 levels were pretty constant [graph 2], and most of that colder period was in the last millennium.
Well worth a look :

October 4, 2012 4:13 pm

Whatever they are smoking, I need to get some… (For analysis only, honest! 😉
Burning trees is supposed to make enough methane to make any difference at all? Do these idiots no NOTHING about swamps and “poo”? In India, they call it “Gobar Gas”. Methane made from fermentation of “poo” from farm animals.
What’s one of the KEY things about getting an effective gobar gas generator running? Warmth. The methanogenic bacteria grow best and produce most gas at warm temperatures (about body temperature is best… guess why…)
So when it warms up naturally what happens to all the “poo” in the soil and all the “poo” in swamps as those methogenic bacteria warm up? Yeah… “swamp gas”…
I’d say “Stuff happens”, except in this case it is poo ‘unhappening’ 😉
So even the rise in methane is highly unlikely to be related to human activity at all.
These loons just MUST put people at the center of the universe… Perhaps we could ask them to go revise Copernicus…

October 4, 2012 4:18 pm

let’s see:
there was the Holocene warming and the development of human agriculture …
there was the Minoan Warm Period and the rise of the Minoan civilisation …
there was the Roman Warm Period and the rise of the Roman civilisation …
then there was the Medieval Warm Period and the rise of European cathedrals
and the Crusades ….
then there was the 20th Century Warm Period and the rise of the Technological and
Space exploring civilisation ….
Seems like warming and human activity go hand in glove …
Which comes first? The chicken or the egg? The warming or growth of human
society? Keep your eye on the pea …

October 4, 2012 6:43 pm

I hate to burst this poor lady’s bubble, but methane just gets gobbled up by little microbes that love the stuff. I wonder if those microbes are ever put in climate models…there could be hundreds of species of them. Honestly, I’d spend money on researching the critters; at least that would provide some conclusion. These microbes are methane regulators, so methane isn’t near as bad as it’s mad out to be.

Steve P
October 4, 2012 9:45 pm

Warmer conditions are better for humans and their civilizations in numerous ways, not least of which is more abundant crops.
The entire CAGW scam teeters on the bogus notion that warmer is worse.

October 5, 2012 2:35 am

mwhite says:
October 4, 2012 at 11:24 am
Fom the GWPF
“The past 5,000 years of the GISP2 temperature history of the Greenland Ice Sheet, adapted from Drake (2012), who denoted the general locations of the Late Bronze Age (LBA), the Roman Warm Period (RWP) and the Medieval Warm Period (MWP) in their original work”

One thing immediately leaps out from the graph. That is that each warm period was less warm than the previous one.
I am surprised that that finding has not received more attention from both climate scientists, the media, and the general public, including keen readers of climate blogs. Surely the long-term trend for warm periods to be less warm is rather worrying?

October 5, 2012 6:40 am

stephen richards says:
October 4, 2012 at 2:08 pm
“I am saddened. The morons are not appearing anymore to defend their god”
They’re only 5 characters away. Just go to grist.

Alan the Brit
October 5, 2012 8:51 am

Edohiguma says:
October 4, 2012 at 7:05 am
You plant vines, & drink wine!!!! much nicer all round! 😉

October 5, 2012 5:49 pm

I’ve just finished a Masters unit on Pompeii and Herculaneum, and the Roman Warm period was discussed,.between 80 BC – AD 250 when the temps were 2 – 3 C warmer than today. Vesuvius erupted in AD 79 and what an eruption! 100 times worse than a Hiroshima atom bomb, it spewed out millions of tons of ash, pumice, hot toxic gases that did the populace in and set back crops etc., miles and miles around for years, plus earthquakes etc.As far away as Africa, Turkey, Syria and Rome of course, If you want to check it out yourselves re the Mt.V , you’ll have to google Mt.Vesuvius as it was mentioned that it cooled the climate for a number of years.
But the Roman Warm Period quote the expers:
prepared by Katy M.Meyers 2012, (C) Center for the Study of Carbon Dioxide and Global Change.

October 5, 2012 5:51 pm

Whoops, should be 250 BC – 450 BC RWP.

October 5, 2012 8:05 pm

I really had a good laugh on this one. My God these Alarmists, will try anything. I am surprised that they have not stated it was a local abnormality; you know confined to the city of Rome just like the MW being local.
This is good for a laugh too!

October 5, 2012 10:51 pm

“in China and Japan culture exploded again, leading to the first novel of mankind.”
You keep saying this. If you are referring to Hikari Genji, then I have to point out, yet again (in the hope that you will notice it) that you are wrong. Hikari Genji was written around 1000. There are Greek and Roman novels from much earlier.

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