PNNL

Abstract

Stratospheric geoengineering by injecting sulfur dioxide into the lower stratosphere has been suggested as a possible means of reducing anthropogenically induced warming. While the impacts of stratospheric aerosol geoengineering on climate change have been investigated through modeling studies in recent decades, few studies have considered the biogeochemical feedbacks resulting from such treatment, and this study is the first to comprehensively characterize the responses and feedbacks of terrestrial ecosystems in an ensemble of strong climate change simulations. These feedbacks can alter the trajectory of atmospheric carbon dioxide levels by storing or releasing additional carbon in terrestrial and marine ecosystems and thus moderate or amplify changes in climate, requiring a modified aerosol injection strategy. We assess the changes in terrestrial biogeochemical feedbacks to climate in response to stratospheric aerosol geoengineering, using model outputs from the Stratospheric Aerosol Geoengineering Large Ensemble project. Results demonstrate that while different regions experience different or even opposite sign terrestrial biogeochemical feedbacks , globally the terrestrial ecosystem becomes a stronger carbon sink, storing an additional 79 Pg C (or 37 ppm CO2-equivalent) from the atmosphere in a geoengineered climate compared to the climate without geoengineering for a high greenhouse gas emissions scenario, which could yield as much as a 4% reduction in atmospheric CO2 mole fraction at the end of the twenty-first century.