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.
Both natural and cultural causes emit methane into the atmosphere.
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?
Humans release the gas into the air due to mimicking of natural causes, and other methods.
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.
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.
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.
- 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 millennia. Nature, 2012; 490 (7418): 85 DOI: 10.1038/nature11461 Note: unless you already subscribe, the Nature article costs $32 (US), but the abstract is free.
Greenhouse Gas Archaeology: Methane Emissions Traced to Roman Times by Shari Maria Silverman is licensed under a Creative Commons Attribution 3.0 Unported License.