Towards a comprehensive, comparative assessment of Climate Engineering schemes - Metrics, Indicators and Uncertainties

• Main Author: Mengis, Nadine
• Format: Thesis
• Language: English
• Published: 2016
• Subjects: Arctic; Arctic Ocean; albedo; Climate change
• Online Access: https://oceanrep.geomar.de/id/eprint/33272/; https://oceanrep.geomar.de/id/eprint/33272/1/Diss_Mengis_doktorarbeit_2016.pdf

Climate Engineering (CE) as an option to prevent dangerous climate change has reached the political debate. For a well informed decision on CE research and deployment in the future, work towards a comprehensive, comparative assessment is needed. In the first part of this thesis, climate impacts and side effects of an artificial Arctic ocean albedo modification scheme are studied. The second part of this thesis presents a parameter sensitivity study on the uncertainty in the response of transpiration to CO2 and implications for climate change. Is the application of indicators used for the historical time period valid for a comprehensive assessment of future climate change? In the third part of the thesis we introduce a methodological approach to systematically evaluate correlation matrices, identifying robust indicators from Earth system variables, to be used in a natural-science based assessment. In the fourth part of this thesis this method is applied to three exemplary CE scenarios: Large-scale afforestation, ocean alkalinity enhancement and solar radiation management. Changes in correlation patterns provide information on which variables might become more relevant under CE scenarios. To enable a comprehensive comparison of the three scenarios, the common correlation matrix is systematically evaluated to identify an indicator set. A preliminary evaluation of the three scenarios based on these indicators remains inconclusive. If the indicators are further aggregated into a metric to reduce the complexity, a ranking of the different scenarios becomes evident. Given all assumptions, we find that overall the RCP4.5 scenario performs ’best’ in staying close to todays climate state. Solar Radiation Management is identified as the ’best’ CE scenario, followed by Ocean Alkalinity Enhancement and Large-scale Afforestation. These analyses advance the natural-science based assessment of CE, which is essential prior to a decision making process.