Quaternary climate changes : a global sensitivity analysis-based emulation approach of a climate model response to astronomical forcing, carbon dioxide concentration, and ice sheet volume
(2015)
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Details
- Authors
- Supervisors
- Crucifix, Michel
- Abstract
- Quaternary climate changes may be comprehended from a modeling perspective by the aid of sensitivity analysis. This is necessary to understand the effect of external and internal factors relevant to the changes both at the global and regional scales. In order to systematically and fully explore the space of these factors and identify their separate and combined effects, a global sensitivity analysis is considered for the first time in this domain. We have provided the analysis of an input-output climate model responses to different forcing. We gave a special care to the presentation and spatial visualization of the sensitivity measures of the different factors with an estimation of their uncertainty, as well as to the determination of the dominant factors.Moreover, we defined for the first time the notion of fingerprints which are characteristic modes extracted from the variation of the sensitivity measures. The phasing between the factors and the climate changes is suggested by the analysis of these fingerprints. Challenges of the global sensitivity analysis using the expensive simulators lead us to combine several techniques: (i) space filling design to sample computer experiments for which we proposed an approach and a new algorithm for sampling in a non hypercube volume defined by the factor, (ii) multivariate analysis to reduce the dimension of the climate model outputs as they are redundant and highly correlated and, (iii) emulation, to approximate the expensive climate simulator. Emulation is necessary to overcome the computational burden caused by the multi-integrals needed for the calculations of the sensitivity measures. The combination of the three methods led to an efficient way to analyze the sensitivity of the complex climate model to the systematic variation in the factors. Compared to standard approaches based on a small number of simulations for well-defined past epochs, we showed that the methodology is robust regarding modeling assumptions, allows us to identify more systematically regions susceptible of experiencing nonlinear climate changes in response to the smooth astronomical forcing and internal factors, and examine the response phase of climate changes to forcing, without having to rely on transient experiment.
- Affiliations
UCLouvain SST/ELI/ELIC - Earth & Climate
Citations
Bounceur, N. (2015). Quaternary climate changes : a global sensitivity analysis-based emulation approach of a climate model response to astronomical forcing, carbon dioxide concentration, and ice sheet volume. https://hdl.handle.net/2078.5/39217