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Anthropogenic Impact on the Earth-Atmosphere System

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Anthropogenic Impact on the Earth-Atmosphere System

The composition of the Earth’s atmosphere is different from that of neighbouring planets such as Mars and Venus, which are apparently lifeless. Fossil records indicate that the atmosphere evolved to its present composition as a result of life. The atmospheric increase of the concentration of molecular oxygen since several billion years indicates that it resulted from photosynthesis after the appearance of life (e.g. Wayne 1992). With the formation of a sufficiently thick ozone layer harmful short wave radiation became attenuated so that life could spread over the Earth’s surface, initially in the oceans still requiring the protecting environment of water, later also on land. According to the Gaia hypothesis the biosphere has played an important role in determining the composition of the atmosphere since life on Earth began (Lovelock 1979). This hypothesis also suggests that the biosphere maintains favourable conditions for life on Earth. On geological timescales the impact of anthropogenic activities on the atmosphere has been of minor significance. However, since the onset of the industrial revolution at the end of the 18th century land use, energy and food requirements for the increasing human population have risen dramatically with the consequence of severe impacts on the Earth environment, especially to the Earth’s atmosphere. Examples relating to significant modifications of the Earth’s atmosphere include (after Crutzen and Stoermer 2000):


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Within a few generations fossil fuels that were generated over several hundred million years have been exhausted. The release of SO2, globally about 160 Tg/year into the atmosphere by coal and oil burning, is at least two times higher than the sum of all natural emissions, occurring mainly as marine dimethyl-sulfide from the oceans.

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30-50% of the land surface has been transformed by human activities; more nitrogen is now fixed synthetically and applied as fertilizer in agriculture than is fixed naturally in all the terrestrial ecosystems.

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The escape into the atmosphere of CO and NOx from fossil fuel and biomass combustion likewise is larger than the natural inputs, giving rise to photochemical ozone (smog) formation and degraded air quality in large regions of the Earth.

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Several climatically important greenhouse gases have substantially increased in the atmosphere: CO2 by more than 30% and CH4 by even more than 100%, accelerating the radiative forcing. CO2 and CH4 are now regulated via the Kyoto Protocol.

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Mankind releases many new and not naturally produced substances into the environment. Some of them, the chlorofluorocarbon gases, have led to the Antarctic ozone hole and would have destroyed much of the ozone layer if no international regulatory (Montreal Protocol) measures to end their production had been initiated.




Considering the major and still growing impacts of human activities on the Earth and the atmosphere on global scales, Crutzen and Stoermer proposed to use the term Anthropocene for the current geological epoch (Crutzen and Stoermer 2000). (see fig. 1-3)

The behavior and composition of troposphere, stratosphere and mesosphere are coupled through dynamic, radiative and chemical processes as indicated in figure 1-3. Overall, the conditions experienced by the biosphere at the Earth’s surface are determined in a complex manner by the physical and chemical processes occurring in all these regions.


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