Northern Hemisphere temperature anomalies during the 1450s period of ambiguous volcanic forcing

Ice core-based estimates of past volcanic eruptions are the main forcing of the last millennium climate model simulations. Understanding the timing and magnitude of eruptions is thus critical for assessing the dynamics of the Earth's climate system. Uncertainty associated with a major event in the 1450s, originally attributed to the South Pacific Kuwae eruption in 1452 and recently shifted to 1458, fundamentally alters model simulations, their comparison with proxy-based climate reconstructions, and any subsequent historical interpretation. Here, we compile a Northern Hemisphere tree-ring network of 25 maximum latewood density chronologies extending back over the past 650+ years to analyze the 1450s temperature deviations. Statistically robust warm season temperature reconstructions from 20 of these records reveal a spatially coherent and exceptional cooling in 1453. Summer cooling ranged from -0.4 degrees C in the Swiss Alps to -6.9 degrees C in the Polar Urals (Russia) and was generally stronger across the Eurasian high latitudes and northwestern North America. Year 1453 also marks the onset of a 15-year cold period during which network mean temperatures ranged from -2.5 degrees C in 1453 to -0.5 degrees C in 1468. In contrast, the years 1459 (-1.0 degrees C) and 1460 (-0.4 degrees C) were not exceptionally cold in the contemporary context. These findings suggest either that the original dating pointing to a major eruption in 1452 (and large-scale cooling in 1453) was correct or that the eruption left no substantial climatic fingerprint in Northern Hemisphere temperature proxies. The latter appears less likely as sulfate aerosol deposits associated with the 1450s event are found in ice cores of both hemispheres.