IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group I: The Physical Science Basis

7.1.5 Coupling the Biogeochemical Cycles with the Climate System

Models that attempt to perform reliable projections of future climate changes should account explicitly for the feedbacks between climate and the processes that determine the atmospheric concentrations of greenhouse gases, reactive gases and aerosol particles. An example is provided by the interaction between the carbon cycle and climate. It is well established that the level of atmospheric CO2, which directly influences the Earth’s temperature, depends critically on the rates of carbon uptake by the ocean and the land, which are also dependent on climate. Climate models that include the dynamics of the carbon cycle suggest that the overall effect of carbon-climate interactions is a positive feedback. Hence predicted future atmospheric CO2 concentrations are therefore higher (and consequently the climate warmer) than in models that do not include these couplings. As understanding of the role of the biogeochemical cycles in the climate system improves, they should be explicitly represented in climate models. The present chapter assesses the current understanding of the processes involved and highlights the role of biogeochemical processes in the climate system.