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Climate of the Past An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/cp-2017-36
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
05 Apr 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Climate of the Past (CP) and is expected to appear here in due course.
Hydroclimate variability in Scandinavia over the last millennium – insights from a climate model-proxy data comparison
Kristina Seftigen1,2, Hugues Goosse2, Francois Klein2, and Deliang Chen1 1Regional Climate Group, Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden
2Georges Lemaître Centre for Earth and Climate Research (TECLIM), Earth and Life Institute, Université catholique de Louvain (UCL), Belgium
Abstract. The integration of climate proxy information with General Circulation Model (GCM) results offers considerable potential for deriving greater understanding of the mechanisms underlying climate variability, as well as unique opportunities for out-of-sample evaluations of model performance. In this study, we combine insights from a new tree-ring hydroclimate reconstruction from Scandinavian with projections from a suite of forced transient simulations of the last millennium and historical intervals from the CMIP5 and PMIP3 archives. Model simulations and proxy reconstruction data are found to broadly agree on the modes of atmospheric variability that produces droughts/pluvials in the region. But despite these dynamical similarities, large differences between simulated and reconstructed hydroclimate time series remain. We find simulated interannual components of variability to be overestimated, while the multidecadal/longer timescale components generally are too weak. Specifically, summertime moisture variability and temperature are weakly negatively associated at inter-annual timescales but positively correlated at decadal timescales, revealed from observational and proxy evidences. On this background, the CMIP5/PMIP3 simulated timescale dependent relationship between regional precipitation and temperature is considerably biased, because the short-term negative association is overestimated, and the long-term relationship is significantly underestimated. The lack of adequate understanding for mechanisms linking temperature and moisture supply on longer timescales has important implication for future projections. Weak multidecadal variability in models also implies that inference about future persistent droughts and pluvials based on the latest generation global climate models will likely underestimate the true risk of these events.

Citation: Seftigen, K., Goosse, H., Klein, F., and Chen, D.: Hydroclimate variability in Scandinavia over the last millennium – insights from a climate model-proxy data comparison, Clim. Past Discuss., https://doi.org/10.5194/cp-2017-36, in review, 2017.
Kristina Seftigen et al.
Kristina Seftigen et al.

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Short summary
Comparisons of proxy data to GCM simulated hydroclimate are still limited and inter-model variability remains poorly characterized. In this study, we bring together tree-ring paleoclimate evidence and CMIP5/PMIP3 model simulations of the last millennium hydroclimate variability across Scandinavia. We explore the consistency between the datasets, and the role of external forcing versus internal variability in driving the hydroclimate changes regionally.
Comparisons of proxy data to GCM simulated hydroclimate are still limited and inter-model...
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