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 human-made.
The results are published in the scientific journal, Nature.
Methane is an important greenhouse gas, which today is partly emitted from natural sources and partly from human activities. The emissions from natural sources varies due to the climate variations. For example, bacteria in wetlands release methane and less is emitted in dry periods as the wetlands shrink.
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