Why are the atmospheric methane levels rising?

Anthropocene

CH4-Concentration in ppb

introduction

Methane (CH4) is a colorless and odorless gas and an important part of the global carbon cycle. It is mainly created by the transformation of organic matter in the absence of oxygen. A large part of methane is produced by the metabolism of microorganisms. The focus here is not on burning, but rather rotting, rotting and digestion. Methane also occurs in deeper layers of the earth's crust. It is Z. B. the main component of natural gas. Methane is also produced when coal is produced.

Methane is a long-lived greenhouse gas. Even if there is a significantly lower atmospheric concentration than CO2 it is one of the three most important greenhouse gases, since CH4 has a 21 times higher global warming potential than CO2.

Historical development

The atmospheric methane concentration (CH4) has increased from 730 ppb (parts per billion) in 1750 to around 1,800 ppb. This is an increase of 150% and like with carbon dioxide (CO2) the highest level for at least 800,000 years.

Around two thirds of all methane emissions today are of human origin. The biggest polluters are, in descending order: livestock, the use of fossil fuels, landfills, rice cultivation and the burning of biomass.

The man-made methane emissions contribute around 16% to global warming. Atmospheric methane is the second most important driver of current climate change.

Agriculture as a methane emitter

Two sectors of agriculture in particular cause a large proportion of anthropogenic methane emissions: cattle breeding and rice cultivation.

In cattle breeding, it is above all the keeping of cattle and sheep: Methane is produced in the stomachs of ruminants, which is released into the atmosphere through belching and excrement. The worldwide increase in meat production is considered to be an important driver of global warming.

The second largest methane emissions from agriculture are caused by the so-called wet cultivation of rice. The strong watering of the soil creates an almost oxygen-free habitat for methane-forming microorganisms. Methane emissions can be reduced by allowing the soil to dry out in the meantime.

Organic carbon in permafrost soils

According to current model calculations, up to 15,000 gigatons of organic carbon are stored in the permanently frozen permafrost soils of the northern hemisphere. This corresponds to about twice the amount of CO2 in the atmosphere. The temperatures on the earth's surface in these regions rise about twice as fast as the global average, in some cases by around 1.8 ° C in the last three decades alone.

The thawing of the permafrost, which is already beginning, could generate large amounts of carbon in the form of methane (CH4) and carbon dioxide (CO2) into the atmosphere and thus accelerate global warming. There is still no clarity about the net effect of the possible emissions, as new plant communities, the CO2 absorb from the atmosphere and also pass it on to the ground.

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Intergovernmental Panel on Climate Change - IPCC (2013): Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Loulergue, L. et al. (2008): Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years. Nature (453), 383-386.

Schuur, E.A.G. et al. (2015). Climate change and the permafrost carbon feedback. Nature, (520), 171-179.

Steffen, W., Broadgate, W., Deutsch, L., Gaffney, O., & Ludwig, C. (2015): The trajectory of the Anthropocene: The Great Acceleration. The Anthropocene Review, 2 (1), 81-98.