Ensemble modeling of the coupled carbon cycle-climate system

• Main Author: Frölicher, Thomas L.
• Other Authors: Joos, F.
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2009
• Subjects: 530 Physics; Archer; Ocean acidification
• Online Access: https://boris.unibe.ch/192495/1/froelicher09phd.pdf; https://boris.unibe.ch/192495/

The overarching theme of this thesis is the impact of anthropogenic carbon emissions on the coupled carbon cycle-climate system. This topic is connected to three specific research questions: (i) the role of internal unforced variability, natural forced variability by explosive volcanism and anthropogenic changes, (ii) the understanding of the long-term consequences of anthropogenic carbon and greenhouse gas emissions, and (iii) the impact of ongoing oceanic carbon uptake and climate change on ocean acidification and dissolved oxygen (O2) depletion. Anthropogenic emissions of carbon dioxide (CO2) and other forcing agents force the atmospheric composition, Earth’s climate, and the chemical state of the ocean towards conditions that have probably not occurred over the past 20 million years (Blackford and Gilbert, 2007) and at a speed that is unprecedented at least during the last 22’000 years (Joos and Spahni, 2008). Today’s atmospheric CO2 concentration of 386 ppm is above the natural range (172 to 300 ppm) of the last 800’000 years (Lüthi et al., 2008). Climate impacts of future anthropogenic CO2 release will persist for millennia (Archer et al., 2009) and poses a significant risk to the human society. This raises questions of adaption to and mitigation of climate change. Besides global warming, anthropogenic carbon emissions cause ocean acidification and oxygen depletion (Meehl et al., 2007; Denman et al., 2007). These processes are less discussed than climate change but potentially with equally far-reaching consequences. A major challenge in climate research is the uncertainty associated with the high level of natural variability in the coupled carbon cycle-climate system. It is still ambitious to identify a current anthropogenic trend in the marine carbon cycle. Understanding and quantifying mechanisms of the carbon cycle-climate system variability is therefore crucial for interpreting observed changes in the context of natural and anthropogenic changes. The publications presented in this study are based on ...