This paper by M. E. Mann, Raymond S. Bradley, and Malcolm K. Hughes reconstructs Northern Hemisphere (NH) temperature patterns over the past millennium using proxy data networks. The focus is on both the reconstructions and the uncertainties associated with them. Despite expanded uncertainties, the results suggest that the late 20th century, particularly the 1990s and 1998, are anomalous in the context of at least the past millennium. The 1990s were the warmest decade, and 1998 was the warmest year, with moderately high confidence. The 20th century warming counters a millennial-scale cooling trend consistent with long-term astronomical forcing. The authors highlight the importance of high-resolution data to better understand spatial and temporal details of climate change over the past millennium.This paper by M. E. Mann, Raymond S. Bradley, and Malcolm K. Hughes reconstructs Northern Hemisphere (NH) temperature patterns over the past millennium using proxy data networks. The focus is on both the reconstructions and the uncertainties associated with them. Despite expanded uncertainties, the results suggest that the late 20th century, particularly the 1990s and 1998, are anomalous in the context of at least the past millennium. The 1990s were the warmest decade, and 1998 was the warmest year, with moderately high confidence. The 20th century warming counters a millennial-scale cooling trend consistent with long-term astronomical forcing. The authors highlight the importance of high-resolution data to better understand spatial and temporal details of climate change over the past millennium.