Effect of increasing CO 2 on the terrestrial carbon cycle

Feedbacks from the terrestrial carbon cycle significantly affect future climate change. The CO2 concentration dependence of global terrestrial carbon storage is one of the largest and most uncertain feedbacks. Theory predicts the CO2 effect should have a tropical maximum, but a large terrestrial sink has been contradicted by analyses of atmospheric CO2 that do not show large tropical uptake. Our results, however, show significant tropical uptake and, combining tropical and extratropical fluxes, suggest that up to 60% of the present-day terrestrial sink is caused by increasing atmospheric CO2. This conclusion is consistent with a validated subset of atmospheric analyses, but uncertainty remains. Improved model…

• NS
  National Science Foundation
• NA
  National Aeronautics and Space Administration
• NC
  National Center for Atmospheric Research
• CI
  California Institute of Technology
• JP
  Jet Propulsion Laboratory