Outcome-based Carbon Sequestration Resource Assessment

Abstract:

Opportunities for carbon sequestration are an important consideration in developing policies to manage the mass balance of atmospheric carbon dioxide (CO₂). Assessments of potential carbon sequestration, like other resource assessments, should be widely accepted within the scientific community and broadly applicable to public needs over a range of spatial and temporal scales. The essential public concern regarding all forms of carbon sequestration is their effectiveness in offsetting CO₂ emissions. But the diverse forms and mechanisms of potential sequestration are reflected in diverse assessment methodologies that are very difficult for decision-makers to compare and apply to comprehensive carbon management. For example, assessments of potential geologic sequestration are focused on total capacities derived from probabilistic analyses of rock strata, while assessments of potential biologic sequestration are focused on annual rates calculated using biogeochemical models. Non-specialists cannot readily compare and apply such dissimilar estimates of carbon storage.

To address these problems, assessment methodologies should not only tabulate rates and capacities of carbon storage, but also enable comparison of the time-dependent effects of various sequestration activities on the mitigation of increasing atmospheric CO₂. This outcome-based approach requires consideration of the sustainability of the assessed carbon storage, as well as the response of carbon-cycle feedbacks. Global models can be used to compare atmospheric CO₂ trajectories implied by alternative global sequestration strategies, but such simulations may not be accessible or useful in many decision settings. Simplified assessment metrics, such as ratios using impulse response functions, show some promise in providing comparisons of CO₂ mitigation that are broadly useful while minimizing sensitivity to differences in global models and emissions scenarios. Continued improvements will require close collaboration between carbon-cycle researchers and those concerned with carbon sequestration resource assessment.