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Greenhouse Gas Archaeology: Methane Emissions Traced to Roman Times

Greenhouse Gas Archaeology: Methane Emissions Traced to Roman Times
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Greenhouse gas archaeology: who knew? It turns out that researchers from the Neils Bohr Institute have been studying it. They’ve examined isotopic methane composition from ice cores taken from the Greenland Ice Sheet. They’ve found that human-caused methane emissions have occurred at least since Roman times. Below is some information about methane emissions, and cultural bits courtesy of ScienceDaily (2012). The parent article appeared in Nature. Both sources are referenced at the base of this post (the Nature one inside of the ScienceDaily one.

Methane Sources

Both natural and cultural causes emit methane into the atmosphere.

Natural Causes

Climate variations generally release methane into the air naturally.

Example: Wetlands’ bacteria release methane into the air. When those marshes shrink, less gas is emitted. A healthy wetland is a smelly one, eh?

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Theler Wetlands Ducks by Shari Maria Silverman is licensed under a Creative Commons Attribution 3.0 Unported License. Bacteria in wetlands release methane gas into the air.

Cultural Causes

Humans release the gas into the air due to mimicking of natural causes, and other methods.

Examples

  • Rice fields, which are wetlands, release methane into the atmosphere.
  • Biomass burning releases the gas too:
    • Burning of forest areas for cultivation, and
    • Burning wood in furnaces.
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    Glacier National Park Fire Remnants by Shari Maria Silverman is licensed under a Creative Commons Attribution 3.0 Unported License. Burning forests release methane into the air. However, the isotopes are heavier than those emitted by wetlands’ bacteria.

Greenhouse Gas Archaeology: Discerning Natural from Cultural Methane Emission

The researchers at the Neils Bohr Institute (University of Copenhagen) found that isotope compositions differed between natural and cultural sources, in general. They found that isotopes released by burning were heavier than those emitted from wetlands. However, scientists can see how far back burning-caused methane release occurred. They can compare their findings to cultural practices at that time. In this way, they conduct greenhouse gas archaeology.

Of course, there are natural forest fires too. The scientists accounted for these.

Analyzing ice cores from over 2000 years ago through the present, they found that methane emissions increased at least 2,100 years ago (Roman times). Below is a synopsis of what the greenhouse gas archaeology has found so far, with reference to European culture.

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Golden Gardens Bonfire by Shari Maria Silverman is licensed under a Creative Commons Attribution 3.0 Unported License. Fires, both naturally- and culturally-caused, release heavier methane isotopes into the atmosphere.

Greenhouse Gas Archaeology: Timeline

  • 2,100 years ago (Roman times): Cultural methane emissions increased.
    • At this time, people burned large amounts of wood fuel for metal work furnaces.
    • However, methane in the atmosphere was still low.
  • 1,000 years ago (Medieval times): Cultural emissions increased significantly.
    • This was a warm and dry period, so wetlands emitted fewer methane gases.
    • However, this decrease was overrun by burning emissions (possibly forest fires).
  • 650 to 150 years ago (A.D 1350 through 1850 [The Little Ice Age]): Both cultural and natural emissions increased.
    • This was a very cold and dry period.
    • Both cultural-caused deforestation and natural forest fires contributed to the methane rise.
  • 200 years ago to present (after A.D. 1800 [Industrial Revolution and HUGE population growth): Cultural emissions increased dramatically.
    • Greenhouse gas archaeology indicates that half of the methane emissions result from human food production, especially cattle and rice fields.
      • The decomposing organic matter emits mass amount of methane into the atmosphere.
    • Also, coal-burning for energy releases a large amount of methane into the air as well.
    • Greenhouse gas archaeology indicates that methane emissions are mighty high.
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Ford Slope Mine by Shari Maria Silverman is licensed under a Creative Commons Attribution 3.0 Unported License. Coal-burning accounts for a lot of methane emissions, after food production such as cattle and rice fields. Pictured is the Ford Slope Mine east of Seattle, which operated during the turn of the 20th Century. It was a very large coal source.


To read more about the greenhouse gas archaeology findings, click on the links within the references below.

References

ScienceDaily
2012   Methane Emissions Can Be Traced Back to Roman Times. ScienceDaily (published online October 3, 2012). Electronic document, http://www.sciencedaily.com/releases/2012/10/121003132322.htm, accessed October 3, 2012. ScienceDaily article is reprinted from materials of the same name provided by the University of Copenhagen on October 3, 2012 (http://www.eurekalert.org/pub_releases/2012-10/uoc-mec100112.php, accessed October 3, 2012). These articles stem from a parent article in Nature:
  • 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.Natural and anthropogenic variations in methane sources during the past two millenniaNature, 2012; 490 (7418): 85 DOI: 10.1038/nature11461 Note: unless you already subscribe, the Nature article costs $32 (US), but the abstract is free.

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Greenhouse Gas Archaeology: Methane Emissions Traced to Roman Times by Shari Maria Silverman is licensed under a Creative Commons Attribution 3.0 Unported License.
 


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