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Abstract. The climate of the Southern Hemisphere (SH) is stronglyinfluenced by variations in the El Niño–Southern Oscillation (ENSO) andthe Southern Annular Mode (SAM). Because of the limited length ofinstrumental records in most parts of the SH, very little is known about therelationship between these two key modes of variability over time. Usingproxy-based reconstructions and last-millennium climate model simulations,we find that ENSO and SAM indices are mostly negatively correlated over thepast millennium. Pseudo-proxy experiments indicate that currently availableproxy records are able to reliably capture ENSO–SAM relationships back to atleast 1600 CE. Palaeoclimate reconstructions show mostly negativecorrelations back to about 1400 CE. An ensemble of last-millennium climatemodel simulations confirms this negative correlation, showing a stablecorrelation of approximately −0.3. Despite this generally negativerelationship we do find intermittent periods of positive ENSO–SAMcorrelations in individual model simulations and in the palaeoclimatereconstructions. We do not find evidence that these relationshipfluctuations are caused by exogenous forcing nor by a consistent climatepattern. However, we do find evidence that strong negative correlations areassociated with strong positive (negative) anomalies in the InterdecadalPacific Oscillation and the Amundsen Sea Low during periods when SAM andENSO indices are of opposite (equal) sign. 

Abstract An extensive new multi-proxy database of paleo-temperature time series (Temperature 12k) enables a more robust analysis of global mean surface temperature (GMST) and associated uncertainties than was previously available. We applied five different statistical methods to reconstruct the GMST of the past 12,000 years (Holocene). Each method used different approaches to averaging the globally distributed time series and to characterizing various sources of uncertainty, including proxy temperature, chronology and methodological choices. The results were aggregated to generate a multi-method ensemble of plausible GMST and latitudinal-zone temperature reconstructions with a realistic range of uncertainties. The warmest 200-year-long interval took place around 6500 years ago when GMST was 0.7 °C (0.3, 1.8) warmer than the 19^thCentury (median, 5^th, 95^thpercentiles). Following the Holocene global thermal maximum, GMST cooled at an average rate −0.08 °C per 1000 years (−0.24, −0.05). The multi-method ensembles and the code used to generate them highlight the utility of the Temperature 12k database, and they are now available for future use by studies aimed at understanding Holocene evolution of the Earth system.