Abstract
Abstract. It is virtually certain that the mean surface temperature of the Earth will continue to increase under realistic emission scenarios, yet comparatively little is known about future changes in climate variability. This study explores changes in climate variability over the large range of climates simulated by the Coupled Model Intercomparison Project Phase 5 and 6 (CMIP5/6) and the Paleoclimate Modeling Intercomparison Project Phase 3 (PMIP3), including time slices of the Last Glacial Maximum, the mid-Holocene, and idealized experiments (1 % CO2 and abrupt4×CO2). These states encompass climates within a range of 12 ∘C in global mean temperature change. We examine climate variability from the perspectives of local interannual change, coherent climate modes, and through compositing extremes. The change in the interannual variability of precipitation is strongly dependent upon the local change in the total amount of precipitation. At the global scale, temperature variability is inversely related to mean temperature change on intra-seasonal to multidecadal timescales. This decrease is stronger over the oceans, while there is increased temperature variability over subtropical land areas (40∘ S–40∘ N) in warmer simulations. We systematically investigate changes in the standard deviation of modes of climate variability, including the North Atlantic Oscillation, the El Niño–Southern Oscillation, and the Southern Annular Mode, with global mean temperature change. While several climate modes do show consistent relationships (most notably the Atlantic Zonal Mode), no generalizable pattern emerges. By compositing extreme precipitation years across the ensemble, we demonstrate that the same large-scale modes influencing rainfall variability in Mediterranean climates persist throughout paleoclimate and future simulations. The robust nature of the response of climate variability, between cold and warm climates as well as across multiple timescales, suggests that observations and proxy reconstructions could provide a meaningful constraint on climate variability in future projections.
Highlights
Knowledge of slow and sustained changes in mean climate conditions is important for understanding climatic risks and uncertainties (IPCC-AR5, 2013)
This study explores changes in climate variability over the large range of climates simulated by the Coupled Model Intercomparison Project Phase 5 and 6 (CMIP5/6) and the Paleoclimate Modeling Intercomparison Project Phase 3 (PMIP3), including time slices of the Last Glacial Maximum, the mid-Holocene, and idealized experiments (1 % CO2 and abrupt4×CO2)
We find no discernible difference in the precipitation scaling between the CMIP5 and CMIP6 models
Summary
Knowledge of slow and sustained changes in mean climate conditions is important for understanding climatic risks and uncertainties (IPCC-AR5, 2013). A core focus of research has been the investigation of major modes of climate variability (Qin et al, 2014), such as the El Niño–Southern Oscillation (Walker and Bliss, 1932; Bjerknes, 1966), and their contemporary change and representation by climate models (Deser et al, 2010, 2012a; Phillips et al, 2014). Their projected changes and relevance for future regional climate evolution remain uncertain (Xie et al, 2015; Christensen et al, 2013). Atmospheric circulation changes contribute strongly to internal climate variability and, inherently, uncertainty in future projections (Thompson et al, 2015)
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