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Combining a new record of bipolar volcanism from Greenland and Antarctic ice cores with records of abrupt climate change derived from the same ice cores, this study provides the most convincing evidence yet of the influence of large volcanic eruptions on long term climate variability, namely Dansgaard-Oeschger warming events. This should garner significant popular interest.

Reviewer 2 of that paper made a clear statement about that paper which can be used at the present level. "This manuscript’s goal is to provide recommendations for how best to develop age models for new ice cores that are anticipated to retrieve ice from 0.8-1.5 Myr ago. As significant resources are being invested to retrieve this ice, the thoughtful advance planning for the creation of these age models is commendable. In proposing specific age modeling strategies, the manuscript also generates useful hypotheses about the types of climate responses that are expected to be found in the new ice cores."

The paper present results of cutting edge climate model simulations and reconstructions of volcanic eruption magnitude and timing to better understand the environmental context of the Ptolemaic era (305-30BCE). This important period of Ancient Egyptian history is known for its material and scientific advances, as well as for episodes of political and social unrest.

This study presents a novel Monte Carlo Empirical Orthogonal Function analysis that combines a dense isotopic proxy network with isotope-enabled climate models to study dynamics and variability of South American Monsoon System (SAMS) over past millennium. This analysis reveals that the leading modes of SAMS variability over the past millennium are regionally stable, arising independently of external forcing (solar, volcanic, orbital). Significant enhancement of the SAMS is accompanied by southward displacement of the South Atlantic Convergence Zone during the Little Ice Age, giving rise to a strengthened South American precipitation dipole. Proxy-model comparison demonstrates outstanding mismatches in centennial-scale hydroclimate departures during the Medieval Climate Anomaly and Little Ice Age from the last millennium mean state. The results of last millennium SASM variability contextualizes modern variability of SASM. The identified proxy data-model mismatch raises a key question to climate simulations of SASM variability, which may attract broad attention from paleoclimate modeling community. Moreover, the reported methodology can be applied to paleoclimate problems of various spatial and temporal scales and is of relevance for the broader geoscience community.

The manuscript presents a reconstruction of global temperature spanning the Holocene, which extends the scope of previous exercises in palaeoclimate data assimilation. The resulting reconstruction presents new insights into changes in global temperature over this period. Most notably, it confirms the results of previous studies that have shown a global cooling trend over the past 6,000 years. It also shows that a cooling trend is found even after allowing for potential biases in the proxies. These results are likely to be of considerable interest to the broader geoscience community.

Huhtamaa et al. assess the socioeconomic consequences of 17th century volcanic eruptions in Fennoscandia. They find that while all the eruptions led to poor grain harvest in the region through their climatic impact, the socioeconomic response varied. They suggest that the micro-regional socioeconomic system modulated the socioeconomic response to each eruption. Such a framework should be used to further our understanding of the impact of volcanic eruptions on societal crises.

The alternation of vegetated and arid Sahara has long attracted wide interest in paleoclimate field. This study presents a suite of highly interesting simulations of the past 190,000 years with a state-of-the-art Earth system model of intermediate complexity. This set of experiments are rigorously designed and analyzed, which allow the authors to make an important discovery of what controls the onset of African Humid Period: i.e. a threshold in orbital forcing, which decreases at elevated CO2 concentration. Moreover, maximum rates of change in simulated vegetation extent during the onset and termination of African Humid Period correlate strongly with the rates of change of the orbital forcing. A factor separation analysis further confirms the dominant role of the orbital forcing in driving the amplitude of precipitation and vegetation extent for past African Humid Period. These results have broad implications to future variability of Sahara climate in response to orbital forcing changes and non-linear earth system feedbacks.