Recent progress in Global Change Research has shown clearly that the Earth's environment is a complex system, defined through intricately linked processes, feedbacks and teleconnections. This makes the conventional scientific approach of investigating only disjunct causal relationships obsolete, and demands a new, integrated way of doing environmental Earth Science.

Observations such as the long-term fluctuations in atmospheric CO2 and CH4, as measured in ice cores, beg the question of cause and effect: Are fluctuations in the biotic greenhouse gases driving the climatic variability, or are externally forced climate variations responsible for changes that result in varying emissions of these gases? Current consensus suggests that there is no simple "either/or" answer to this question, but that the biota and their geophysical and geochemical environments have coevolved, resulting in a multitude of complex interactions and feedbacks.

Atmospheric processes, such as physical climate variability and chemical deposition, are major constraints on biogeochemical cycles, natural as well as anthropogenic ones. For example, interannual variability of carbon uptake at all scales is influenced by variations in climate and the related feedbacks to physiology and productivity. The deposition of gases and aerosols from the atmosphere can also strongly influence ecosystem functioning, sometimes acting as fertilizers, sometimes as toxic substances.