The enrichment of the atmosphere with CO₂ and soluble N-compounds is a given, unquestioned part of global change.

• The atmospheric CO₂ concentration has increased by c. 30 % over the past 200 years from 280 to 370 ppm. Most of this increase has occurred during the last 50 years (Fig. 1).

• Since the early 1980s, anthropogenic nitrogen "fixation", i.e. the production of gaseous soluble N-compounds (NO_x, NH₃) has exceeded the global natural N-fixation. In some areas of the globe ecosystem N-input has increased 10-20 fold during the past 100 years (Fig. 2).

• To a large extent, the mean global atmospheric warming of 0.6 K observed during the last century has been driven by the anthropogenic release of greenhouse gases such as CO₂. Warming has been ca. 1 K in the European Alps and several K in some subarctic mountains. These thermal changes affect other components of the climate system as well (precipitation, cloudiness, wind) (Fig. 3).
   

1 - The 420'000 year course of atmospheric CO₂ concentration as reconstructed from antarctic ice cores. Note the 180-290 ppm range from which current trends significantly deviate (Petit et al. 1999).

2 - Anthropogenic vs. natural N-fixation (Vitousek 1994).

3 - Climate warming: a comparison of global trends in mean surface temperature anomalies with those averaged for eight high elevation sites in the Alps (smoothed out with a 5-year filter) (Beniston et al. 1997).

29 August 2011
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