RESUMEN
Volcanic eruptions contribute to climate variability, but quantifying these contributions has been limited by inconsistencies in the timing of atmospheric volcanic aerosol loading determined from ice cores and subsequent cooling from climate proxies such as tree rings. Here we resolve these inconsistencies and show that large eruptions in the tropics and high latitudes were primary drivers of interannual-to-decadal temperature variability in the Northern Hemisphere during the past 2,500 years. Our results are based on new records of atmospheric aerosol loading developed from high-resolution, multi-parameter measurements from an array of Greenland and Antarctic ice cores as well as distinctive age markers to constrain chronologies. Overall, cooling was proportional to the magnitude of volcanic forcing and persisted for up to ten years after some of the largest eruptive episodes. Our revised timescale more firmly implicates volcanic eruptions as catalysts in the major sixth-century pandemics, famines, and socioeconomic disruptions in Eurasia and Mesoamerica while allowing multi-millennium quantification of climate response to volcanic forcing.
Asunto(s)
Clima , Temperatura , Erupciones Volcánicas/historia , Aerosoles/análisis , Américas , Regiones Antárticas , Atmósfera/química , Berilio , Radioisótopos de Carbono , Desastres/historia , Europa (Continente) , Groenlandia , Historia Antigua , Historia Medieval , Hielo/análisis , Radioisótopos , Datación Radiométrica , Estaciones del Año , Azufre , Factores de Tiempo , Árboles/anatomía & histología , Árboles/crecimiento & desarrollo , Clima TropicalRESUMEN
Time scales are derived, from radiocarbon dating of pollen diagrams, for Neolithic land clearance at three Irish sites. Three stages are distinguished beginning in the 4th millennium B.C.: stage A, clearance and farming (possibly arable), 100 to 400 years; stage B, farming (possibly pastoral), 150 to 200 years; and stage C, forest regeneration, 50 to 100 years.
RESUMEN
Tephra-linked pollen diagrams from lowland raised peats at three sites in the north of Ireland show extensive landscape changes between A.D. 750 and A.D. 1150. By A.D. 860 woodland had been cleared and agricultural activity was widespread but, by the start of the twelfth century, woods had regenerated and agriculture had declined. The gap in the Irish dendrochronological record between A.D. 730 and A.D. 850 is bridged by timbers from corn grinding mills, strengthening the case for spreading arable agriculture at this time.