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Background and Motivation

Climate-induced changes in the terrestrial biosphere and the ocean modulate the release and uptake of carbon dioxide and this, in turn, alters atmospheric composition and influences the climate. This is known as the climate-carbon cycle feedback. The Coupled Carbon Cycle Climate Model Intercomparison Project (C4MIP), using models of the terrestrial and ocean carbon cycles inside ocean-atmosphere general circulation models, has shown that the carbon cycle-climate feedback appears to be positive BUT there is great uncertainty about the magnitude. It is important to know the magnitude of this feedback because it affects the amount of carbon dioxide that can be emitted in the future in order to stabilize the concentration of CO2 at a given level. There are projects attempting to reduce these uncertainties through systematic evaluation of carbon cycle models against observations of the contemporary carbon cycle. An alternative approach is to use knowledge about past variations in climate and CO2 to provide additional constraints. PCMIP is an international activity that will combine carbon cycle and palaeoclimate modelling with ice-core and palaeoclimate records to quantify the carbon-cycle climate feedback.

The activity will use the power of modelling to demonstrate what processes contribute to this feedback on different time scales, and how knowledge of these processes may contribute to the understanding of the contemporary carbon cycle and climate. PCMIP will build on the ongoing work of the Palaeoclimate Modelling Intercomparison Project (PMIP), which is investigating climate changes on glacial-interglacial timescales as well as during the last millennium.

PCMIP is an international activity sponsored by the IGBP core projects Analysis, Integration and Modelling of the Earth System (AIMES) and the Palaeoclimate Commission (PALCOMM) of the International Quaternary Association (INQUA).

Reconstruction of the atmospheric CO<sub>2</sub> concentration over the last
millennium from the EPICA Dronning Maud Land and South Pole ice cores
(Siegenthaler et al., 2005), the Law Dome ice cores and firn air samples
(MacFarling-Meure et al., 2006), and the Cape Grim ambient air
measurements (Francey et al., 2003).

Co-ordination Team

Ayako Abe-Ouchi, Pierre Friedlingstein, Sandy P. Harrison, I. Colin Prentice.
Contact Co-ordinators

Website Information

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