Raimund Muscheler
Professor
Causal links of past climate change in Coupled Model Intercomparison Project Phase 5 climate models
Author
Summary, in English
This thesis uses the Granger causality test to investigate the impacts of external forcings on subdecadal variability of regional near-surface air temperature (SAT) during the past millennium (period 850-1850). In addition, the role of solar forcing on low-frequency variability of the North Atlantic is examined and the two-way causal relationship between the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) is evaluated. The investigations are mainly based on the output from the Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations.
The results of this thesis support the conclusion for robust impact of volcanic forcing on SAT during preindustrial times of the past 1000 years. Besides, the results indicate that there is solar signal in SAT response of the tropical and subtropical regions whereas the influence of greenhouse gases radiative forcing on regional SAT is weak and uncertain. In addition, solar forcing might have an influence, at multi-centennial time scales, on the North Atlantic winter sea surface temperatures while the connection between solar forcing and the North Atlantic Oscillation is weak in the models. The results for the investigation of the causal impact of ENSO on the IOD show that this impact is weaker in numerous models than the result in reanalysis datasets, whereas the influence of the IOD on ENSO is robust for most models and reanalysis datasets.
Overall, the findings in this thesis contribute to the knowledge of the influence of external forcings on regional climate change and help us to better understand the two-way causal relationship between ENSO and the IOD.
Department/s
- Quaternary Sciences
- MERGE: ModElling the Regional and Global Earth system
Publishing year
2016
Language
English
Publication/Series
Lundqua thesis
Issue
83
Document type
Dissertation
Publisher
Lund University, Faculty of Science, Department of Geology, Quaternary Sciences
Topic
- Climate Research
- Meteorology and Atmospheric Sciences
- Geosciences, Multidisciplinary
Keywords
- solar forcing
- volcanic forcing
- greenhouse gases radiative forcing
- Granger causality
- near-surface air temperature
- ENSO
- IOD
- CMIP5
- North Atlantic
Status
Published
Project
- Causal links of past climate change in Coupled Model Intercomparison Project Phase 5 climate models
Supervisor
- Jesper Sjolte
- Raimund Muscheler
- Dan Hammarlund
- Svante Björck
ISBN/ISSN/Other
- ISSN: 0281-3033
- ISBN: 978-91-87847-25-7
- ISBN: 978-91-87847-24-0
Defence date
21 October 2016
Defence time
13:15
Defence place
Geocentre II, lecture hall “Pangea”, Sölvegatan 12, Lund
Opponent
- Qiong Zhang (Senior lecturer)