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Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model

An Erratum to this article was published on 07 December 2000


The continued increase in the atmospheric concentration of carbon dioxide due to anthropogenic emissions is predicted to lead to significant changes in climate1. About half of the current emissions are being absorbed by the ocean and by land ecosystems2, but this absorption is sensitive to climate3,4 as well as to atmospheric carbon dioxide concentrations5, creating a feedback loop. General circulation models have generally excluded the feedback between climate and the biosphere, using static vegetation distributions and CO2 concentrations from simple carbon-cycle models that do not include climate change6. Here we present results from a fully coupled, three-dimensional carbon–climate model, indicating that carbon-cycle feedbacks could significantly accelerate climate change over the twenty-first century. We find that under a ‘business as usual’ scenario, the terrestrial biosphere acts as an overall carbon sink until about 2050, but turns into a source thereafter. By 2100, the ocean uptake rate of 5 Gt C yr-1 is balanced by the terrestrial carbon source, and atmospheric CO2 concentrations are 250 p.p.m.v. higher in our fully coupled simulation than in uncoupled carbon models2, resulting in a global-mean warming of 5.5 K, as compared to 4 K without the carbon-cycle feedback.

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Figure 1: Modelled and observed interannual variability in the atmospheric CO2 concentration.
Figure 2: Budgets of carbon during the fully coupled simulation.
Figure 3: Effect of climate/carbon-cycle feedbacks on CO2 increase and global warming.
Figure 4: Effect of global warming on changes in land carbon storage.

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We thank J. Mitchell and G. Jenkins for comments on earlier versions of the manuscript. This work was supported by the UK Department of the Environment, Transport and the Regions.

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Correspondence to Peter M. Cox.

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Cox, P., Betts, R., Jones, C. et al. Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model. Nature 408, 184–187 (2000).

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