The carbon cycle is a key component of the climate system and supporting carbon cycle development, simulations and analysis is a central strand of CRESCENDO.

By Chris Jones (MOHC, UK). 23-24 May, 2016. UPMC Jussieu campus, Paris, France

In May, 15 scientists, including representative from 6 CRESCENDO partners met in Paris to discuss and finalise experiment plans for C4MIP: the Coupled Climate-carbon cycle Model Intercomparison Project (

Chris Jones from the Met Office Hadley Centre, co-chair of C4MIP and CRESCENDO RT lead for Evaluation (RT2), organised the workshop which was supported by CRESCENDO travel funding and kindly hosted by CRECENDO partner, IPSL in Paris. The workshop was targeted at European carbon cycle modellers: “We thought about hosting the meeting in Exeter”, Chris explained, “but we wanted to minimise travel time and carbon emissions which made Paris – a much more central and accessible venue – the perfect option.”

At the meeting, two participants. Chris Jones and Stephen Sitch, made remote presentations to the land and ocean biogeochemistry session of the Japan Geoscience Union in Tokyo ( The group in Paris were able to join the Tokyo session via a Webex link including sharing presentations and engaging in a lively discussion session after the talks. On the second day we also had a remote presentation from the UK by CRESCENDO WP8 lead, Peter Cox, on Emergent Constraints in the earth system.

June_2016_DECK_CMIP6_hist_vs_C4MIP_runsOne central discussion and outcome of the workshop was the adoption of an additional experiment to be added to our plans for CMIP6. In light of the Paris Agreement ( we wanted to examine in more detail how the carbon cycle behaves under a low mitigation scenario. Therefore we have added a new experiment to our plans: an analysis of carbon cycle feedbacks in the “SSP5-3.4-OS” overshoot scenario. This overshoot scenario follows SSP5-8.5 up to 2040 followed by aggressive mitigation to reduce emissions to zero by about 2070 followed by substantial negative global emissions thereafter. The carbon cycle response to such a peak-and-decline CO2 pathway is likely to differ from the response to continued strong increases in CO2.

CRESCENDO WP12 will support delivery of C4MIP simulations.

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