Methane emissions traced back to Roman times

Oct 03, 2012
The isotope curve shows that the emissions of the greenhouse gas methane had several peaks in the last 2,100 years. 1: During Roman times, where a lot of wood was burned for heating and for the processing of metals. 2: During the warm Middle Ages, where forests caught on fire. 3: In the "Little Ice Age", which was a very cold and dry period. 4: The methane concentration has increased dramatically since approx. the year 1800, when industrialization took off and triggered energy and food production, for example, rice fields. Credit: NBI

Emissions of the greenhouse gas methane into the atmosphere can be traced back thousands of years in the Greenland ice sheet. Using special analytical methods, researchers from the Niels Bohr Institute, among others, have determined how much methane originates from natural sources and how much is due to human activity. The results go all the way back to Roman times and up to the present, where more than half of the emissions are now man-made. The results are published in the scientific journal Nature.

Methane is an important greenhouse gas, which today is partly emitted from and partly from human activities. The emissions from natural sources varies due to the . For example, bacteria in wetlands release methane and less is emitted in dry periods as the wetlands shrink.

Emissions of methane into the atmosphere also come from human actions. For example, methane is emitted from rice fields, which are of course wetlands, and methane is emitted from biomass burning, either from burning of forest areas for cultivation or the use of wood in furnaces. Energy production through also produces methane gases. But how can you determine where the comes from?

Different sources can be traced

"The different sources of methane have different isotopic compositions. The methane produced by the burning of biomass, like wood, contains more of the heavier isotope (carbon-13) relative to the lighter isotope (carbon-12), than methane which is produced in wetlands," explains Professor Thomas Blunier, Centre for and Climate at the Niels Bohr Institute at the University of Copenhagen. The researchers have measured the of the methane in ice cores that are drilled up from the Greenland ice cap at the NEEM project in northwestern Greenland. The ice cap is formed from snow that falls year after year and remains, gradually getting compressed into ice. The ice contains tiny air bubbles from the atmosphere in the snow that fell, and by analysing the composition of the air you can get a climate curve, which tells you about both the annual temperature and methane content.

The question is how far back in history man has had an impact on the methane concentration in the atmosphere?

Forest fires and burning wood emits "heavy" methane, which can be traced in the analyses of ice cores in the ice cap on Greenland. Credit: John Tuttle, FWS

Methane emissions are peaking now

"We have analysed the methane composition more than 2,000 years back in time. We can see that already 2,100 years ago during , some cultures were spreading out and burning large amounts of wood for fuel in furnaces to work with metals that required intense heat to process. But the level was still low. The next significant increase was during the Middle Ages around 1,000 years ago. It was a warm period and it was dry so there were presumably many forest fires that emitted methane while the wetlands dwindled and reduced from that source. We also find emissions from natural forest fires and deforestation during the so-called 'Little Ice Age' (between 1350 and 1850), which was a very cold and dry period, Emissions of methane increased dramatically from around 1800, when the industrial revolution took off and where there occurred a large increase in population," explains Thomas Blunier.

Rice fields are wetlands and contribute to about 20% of methane emissions into the atmosphere today. Credit: NBI

The analyses show that from around the year 1800 there are large increases that are man-made. Approximately half originates from the production of food – especially rice fields and cattle. Then a lot is emitted from the decomposition of organic materials that are deposited and methane is emitted from burning coal for energy.

"The extent to which our ancestors were able to influence the emissions of methane with their activities is surprising. The general trend from 100 BCE to the year 1600 shows a correlation between the increase in the appropriation of land for cultivation and the emission of the biogenic methane. Today, half of the emissions stem from human activities," says Thomas Blunier.

Explore further: Mysterious source of ozone-depleting chemical baffles NASA

More information: 'Natural and anthropogenic variations in methane sources during the past two millennia',
Célia 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 en T. Röckmann,
Nature 2012, DOI: 10.1038/nature11461

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User comments : 19

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ScooterG
1.7 / 5 (24) Oct 03, 2012
I went to the website of this university and spent some time reading about their climate study efforts. Nowhere did I find a prejudice towards AGW. Either I missed it, it is not there, or these people have learned to hide it.

I'm going to have to dismiss this group and their research because 1) I've been driven to cynicism by the plethora of AGW junk science and 2) this group did not make any effort to distance themselves from AGW junk science.

Cynicism occurs when the value of credibility is taken lightly. Restoration of credibility - if it can happen at all - will take generations.

Actions have consequences. Remember the NBC Dateline exploding gas tank? Remember the Alar scam? Remember the spotted owl scam? Remember the Dan Rather/national guard libel/slander?
packrat
2.1 / 5 (19) Oct 03, 2012
This doesn't make a lot of sense to me. There were people around the entire time and not just 2000 and 1000 years ago. It doesn't say anything about the rest of the world which was also populated and used just as much fuel as the Romans for the same reasons. Why do these researchers always tend to leave everyone else out when doing these research projects?
StarGazer2011
1.7 / 5 (17) Oct 03, 2012
This doesn't make a lot of sense to me. There were people around the entire time and not just 2000 and 1000 years ago. It doesn't say anything about the rest of the world which was also populated and used just as much fuel as the Romans for the same reasons. Why do these researchers always tend to leave everyone else out when doing these research projects?


Part of it is national government funding, research on other countries is less likely to attract grants; part is parochialism (who wants to get a TSA patdown?).
Also since this is the CAGW industry, small sample sizes are preferred as they can be more easily controlled and 'adjusted' to give the 'right' politically correct and profitable answer.
Im not clear on this research, methane falls apart pretty readily and anyone know why fire causes higher C13 than the same wood processed by microbes?
VendicarD
4.1 / 5 (13) Oct 03, 2012
It appears that we have yet another hockey stick.

Their numbers are growing faster than the number of pregnant 12 year olds at a Hillbilly Howdown.
VendicarD
3.3 / 5 (14) Oct 03, 2012
ScooTard is right. Overwhelming evidence is evidence of the contrary.

That is why no one should believe that the earth rotates around the sun or that 1 plus 1 = 2.

VendicarD
3.5 / 5 (19) Oct 03, 2012
I find it continually astonishing that people like PacRat are incapable of reading yet believe they have something to add.

Methane levels were measured from ice cores, you Moron.

"It doesn't say anything about the rest of the world which was also populated" - PacRat
NotParker
1.4 / 5 (18) Oct 03, 2012
Typical dumb greenies. Ban coal. Encourage methane production.

"TOKYO -- IHI Corp. a Japanese maker of heavy machinery, acquired as much as 50 percent stakes in five power plants in California from Exelon Corp.

IHI bought shares in three biomass power plants and two coal-fired stations, which the company plans to convert to biomass, IHI said in a statement today without disclosing any financial details.

The two coal-fired plants are Rio Bravo Jasmin and Rio Bravo Poso stations, each with a capacity of 33 megawatts, according to the statement.

The rest of the plants, all biomass, are the 25-megawatt Chinese Station, Rio Bravo Rocklin and Rio Bravo Fresno, both with 28 megawatts of capacity, the statement said."

http://www.renewa...-biomass

mrtea
3.2 / 5 (9) Oct 03, 2012
As usual VendicarD, you resort to childish name calling. You are the main reason I don't bother engaging in these discussions. You make trolls look good by comparison.
JoeBlue
1.5 / 5 (17) Oct 04, 2012
Why is that it's assumed that the Ice Cores automatically display what was going on across the globe? Isn't it telling when these same people are claiming that the Artic Ice is melting, but the Antarctic Ice is expanding that there is no real mechanism for global distribution for any of these finding's?

Every article of this nature assumes that distribution is always even across the globe, but this is something that they have never been able to prove. To add that they make conclusions based on spurious evidence without having peer review of the evidence and findings.

No one can take this crap seriously until they start taking the rest of the community seriously and answer the questions that have been made.
unknownorgin
1.3 / 5 (15) Oct 04, 2012
This study is flawed because the carbon from forests or wetlands can only come from CO2 in the atmosphere so the isotope ratio should be the same and both isotopes are chemicaly the same. The only thing the study can claim is that average methane levels have increased.
Sherrin
3.3 / 5 (7) Oct 04, 2012
It used to be convention in scientific literature that acronyms, or abbrevviations, such as 'BP' were defined in brackets immediately following the first use of the acronym. Nowadays, it is assumed the reader 'knows everything'. While I could easily go (and have gone) to Google to track down a meaning for 'BCE', I wonder why the old convention has now been dropped? Laziness on the part of the editor, I suspect.
rubberman
3.8 / 5 (10) Oct 04, 2012
This study is flawed because the carbon from forests or wetlands can only come from CO2 in the atmosphere so the isotope ratio should be the same and both isotopes are chemicaly the same. The only thing the study can claim is that average methane levels have increased.


From the article: ""The different sources of methane have different isotopic compositions. The methane produced by the burning of biomass, like wood, contains more of the heavier isotope (carbon-13) relative to the lighter isotope (carbon-12), than methane which is produced in wetlands," explains Professor Thomas Blunier.

Reading 101 kids.

Also a good point Sherrin, I too find myself having to check acronyms I haven't seen before because they aren't defined when used.
NotParker
1.7 / 5 (12) Oct 04, 2012

From the article: ""The different sources of methane have different isotopic compositions. The methane produced by the burning of biomass, like wood, contains more of the heavier isotope (carbon-13) relative to the lighter isotope (carbon-12), than methane which is produced in wetlands," explains Professor Thomas Blunier.


Or people ate more millet.

1) There are C3 and C5 pathway plants. C3 plants have an affinity for C12, but C4 plants have an affinity for C13.

These include the food crops maize, sugar cane, millet, and sorghum and about 7600 other plants. (Wikipedia)

"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 person was therefore eating a whole bunch of C4 resources - millet, sorghum, or animals foddered on those grains."

http://www.powere...ire.html
VendicarD
3.6 / 5 (9) Oct 04, 2012
Oh, lookie... Another illiterite who responds to an article based it's bare reading of the title and who avoided reading the content.

"This study is flawed because the carbon from forests or wetlands" - unknownorigin

It is amazing that people like unknown manage to feed themselves.
VendicarD
4.2 / 5 (10) Oct 04, 2012
Probably because the atmosphere is well mixed.

You might have noticed this thing moving the tree branches around.

It is called wind.

Pay attention next time you are outside and you might notice it.

"Why is that it's assumed that the Ice Cores automatically display what was going on across the globe?" - JoeToe

There is no wind in the X-Box. Perhaps that is your source of error.
VendicarD
3.7 / 5 (10) Oct 04, 2012
Translation. JoeToe has never had the explanation randomly presented to him. He has never looked. Doesn't know how to look. Doesnt' care to look, and wouldn't understand the evidence if he did.

Hence to him, it must be unproven in science.

"Every article of this nature assumes that distribution is always even across the globe, but this is something that they have never been able to prove." - JoeToe

Pathetic.
VendicarD
2.7 / 5 (9) Oct 04, 2012
I pity da foo, who call's itself Mr. T.

Sadly It believes that public displays of innumeracy and illiteracy are to be defended and commended.

Is it any wonder why the American is dead as a nation?
rubberman
3.8 / 5 (10) Oct 04, 2012
"1) There are C3 and C5 pathway plants. C3 plants have an affinity for C12, but C4 plants have an affinity for C13."

OK. Ahem, good try. But the C4/C3 uptake doesn't correlate to methane production, it determines the vehicle for the photosynthetic process.

http://wyrdscienc...biology/

The difference in carbon isotopes is an indication of whether the methane was produced under aerobic or anaerobic conditions.
NotParker
1.5 / 5 (8) Oct 04, 2012

OK. Ahem, good try. But the C4/C3 uptake doesn't correlate to methane production, it determines the vehicle for the photosynthetic process.

http://wyrdscienc...biology/

The difference in carbon isotopes is an indication of whether the methane was produced under aerobic or anaerobic conditions.


"The different isotope ratios for the two kinds of plants propagate through the food chain, thus it is possible to determine if the principal diet of a human or an animal consists primarily of C3 plants (rice, wheat, soybeans, potatoes) or C4 plants (corn, or corn-fed beef) by isotope analysis of their flesh and bone collagen. Similarly, marine fish contain more 13C than freshwater fish, with values approximating the C4 and C3 plants respectively."

http://en.wikiped...ignature

When C4 plants rot, more C13 methane. When humans and animals that ate C4 plants rot, more C13 methane.