labs_title

Caldeira Lab Research:Land Plants, Carbon, and Climate/Energy, Global Carbon Cycle, and Climate

Increase of carbon cycle feedback with climate sensitivity: results from a coupled climate and carbon cycle model

G. Bala, S. Thompson, A. Mirin, M. Wickett, K. Caldeira & C. Delire

Previous studies have shown that climate change and the carbon cycle have a positive feedback relationship: as temperatures rise, the carbon cycle changes, resulting in greater warming. Here the sensitivity of this relationship is investigated using various climate sensitivities under the same emissions scenario.


G.Bala, S. Thompson, A. Mirin, M. Wickett, K. Caldeira and C. Delire Increase of carbon cycle feedback with climate sensitivity: results from a coupled climate and carbon cycle model Tellus B 57 (2) 153 -- 163 DOI: 10.1111/j.1600-0889.2005.00135.x, 2005.

Decrease in land uptake: Increasing climate sensitivity leads to a reduction of land uptake. A reduction in land uptake fosters higher atmospheric carbon concentration.

Abstract

Coupled climate and carbon cycle modeling studies have shown that the feedback between global warming and the carbon cycle, in particular the terrestrial carbon cycle, could accelerate climate change and result in greater warming. In this paper we investigate the sensitivity of this feedback for year 2100 global warming in the range of 0K to 8K. Differing climate sensitivities to increased CO2 content are imposed on the carbon cycle models for the same emissions. Emissions from the SRES A2 scenario are used. We use a fully coupled climate and carbon cycle model, the INtegrated Climate and CArbon model (INCCA), the NCAR/DOE Parallel Climate Model coupled to the IBIS terrestrial biosphere model and a modified OCMIP ocean biogeochemistry model. In our integrated model, for scenarios with year 2100 global warming increasing from 0K to 8K, land uptake decreases from 47% to 29% of total CO2 emissions. Due to competing effects, ocean uptake (16%) shows almost no change at all. Atmospheric CO2 concentration increases are 48% higher in the run with 8K global climate warming than in the case with no warming. Our results indicate that carbon cycle amplification of climate warming will be greater if there is higher climate sensitivity to increased atmospheric CO2 content; the carbon cycle feedback factor increases from 1.13 to 1.48 when global warming increases from 3.2K to 8K.