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SCIAMACHY's View of the Earth's Atmosphere

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3. SCIAMACHY’s View of the Changing Earth’s Environment

During the years since SCIAMACHY’s launch in 2002, numerous scientific results from the SCIAMACHY mission have been derived, clearly demonstrating the high ‘return on investment’ of this mission. New and exciting insights into the Earth-atmosphere system are obtained. They contribute significantly to atmospheric physics and chemistry, as well as to global climate change research. Many scientific groups at various institutes in Europe and abroad were and are actively involved in the analysis of the data. The following chapter highlights some of the most exciting findings based on operational and scientific data analysis. The chapter is based on material collected for the book "SCIAMACHY - Exploring the Changing Earth’s Atmosphere" (Gottwald and Bovensmann 2011, published by Springer, ISBN 978-90-481-9895-5 ), where the interested reader will find even more highlights of the SCIAMACHY mission.

The interested reader is further referred to the internet resources:

where SCIAMACHY data products, scientific results and related detailed information about our atmosphere can be found.

3.1 Tropospheric Composition – Greenhouse Gases

SCIAMACHY measurements provide information on tropospheric constituents as solar radiation penetrates the atmosphere down to the surface. Our civilisation imposes a significant stress upon the troposphere. Concentrations of greenhouse gases are increasing and have been identified as the source of global warming. SCIAMACHY permits not only the monitoring of the global status of the major greenhouse gases but also the retrieval of knowledge about the distribution of their sources such as e.g. densely populated regions or wetlands.

Carbon Dioxide – CO2

CO2, the most important anthropogenic greenhouse gas, is regulated by the Kyoto Protocol and can be considered as a synonym for the impact of industrialisation on our environment. In pre-industrial times, CO2 mixing ratios dating back several thousands of years were about 300 ppm at maximum. Present values are around 390 ppm, i.e., 30% higher, with the increase mainly attributed to the past 50 years – a clear indication of an anthropogenic effect. Carbon dumped into natural sinks over millions of years is now being released into the atmosphere by fossil fuel burning (oil, coal, gas). In addition, other anthropogenic activities such as deforestation destroy important CO2 sinks and reduce nature’s ability to recycle atmospheric CO2 efficiently. A thorough study of carbon dioxide is therefore necessary to understand the global carbon cycle and to predict how greenhouse gas concentrations evolve with time. Currently, about 50% of the emitted CO2 remains in the atmosphere, the other half is taken up by the oceans and in the biosphere. Photosynthesis extracts carbon dioxide from the troposphere over land. Thus, large forest areas act as a CO2 sink. The North American and Siberian boreal forests in summer are examples for such extended CO2 sinks. These sink regions can be observed by SCIAMACHY, as illustrated in Fig. 3-1 displaying atmospheric CO2 levels from April to June compared to July to September, where CO2 concentrations are lower due to uptake by the terrestrial biosphere. This seasonal ‘CO2 breathing’ is superimposed on the steady increase of atmospheric CO2 with much higher concentrations in 2009 than in 2003. Both phenomena can be clearly observed by SCIAMACHY.

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