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Title: Modelling the recovery of the atmosphere from fossil fuel perturbation and quantifying its associated uncertainty
Author: Britton, Clare
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2006
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This thesis addresses the response of the atmosphere to past and possible future anthropogenic CO2 emissions on timescales of up to a million years. Deep marine sediments and weathering were added to an efficient global carbon cycle model. The effect of enhanced weathering on atmosphere CO2 response to fossil fuel CO2 release was investigated for a range of emissions scenarios. 11 parameters in the ocean and sediment system were allowed to vary and the model was calibrated with atmospheric CO2 data using a Bayesian methodology. This model was then used to assess the uncertainty in atmospheric CO2 response with and without biotic feedbacks on carbonate and silicate weathering. The enhancement of weathering due to increases in CO2 and temperature is found to significantly accelerate the drawdown of CO2 on timescales of 104-105 years, although it will till take > 106 years for the CO2 level to stabilise. Enhanced weathering has most effect when all sediments in the ocean are dissolved. Timescale of response in the atmosphere depends on the weathering formulation used. Silicate weathering is required to return CO2 to pre-industrial levels. Calibrating with data improved the model response as mean peak CO2 levels were ~235ppmv lower than results from previous studies. Uncertainty in CO2 response due to parameter uncertainty is >500ppmv in some cases, this uncertainty peaks on the millennial timescale and decreases thereafter. The range of uncertainty in CO2 response for a single emissions scenario encompasses the range of uncertainty due to varying emissions from 300 to 5000GtC in other studies. The time for the atmosphere to return to current levels of CO2 is also greatly uncertain, with the earliest possibility occurring at ~ year 10,000 but most likely occurrence at ~ year 100,000.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available