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Tree rings reveal globally coherent signature of cosmogenic radiocarbon events in 774 and 993 CE.

Ulf BüntgenLukas WackerJ Diego GalvánStephanie ArnoldDominique ArseneaultMichael BaillieJürg BeerMauro BernabeiNiels BleicherGretel BoswijkAchim BräuningMarco CarrerFredrik Charpentier LjungqvistPaolo CherubiniMarcus ChristlDuncan A ChristiePeter W ClarkEdward R CookRosanne D'ArrigoNicole DaviÓlafur EggertssonJan EsperAnthony M FowlerZe'ev GedalofFabio GennarettiJussi GrießingerHenri Grissino-MayerHåkan GruddBjörn E GunnarsonRashit HantemirovFranz HerzigAmy E HesslKarl-Uwe HeussnerA J Timothy JullVladimir V KukarskihAlexander KirdyanovTomáš KolářPaul J KrusicTomáš KynclAntonio LaraCarlos LeQuesneHans W LinderholmNeil J LoaderBrian LuckmanFusa MiyakeVladimir S MyglanKurt NicolussiClive OppenheimerJonathan G PalmerIrina P PanyushkinaNeil PedersonMichal RybníčekFritz H SchweingruberAndrea SeimMichael SiglOlga V Churakova SidorovaJames H SpeerHans-Arno SynalWilly TegelKerstin TreydteRicardo VillalbaGreg WilesRob WilsonLawrence J WinshipJan WunderBao YangGiles H F Young
Published in: Nature communications (2018)
Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the 14C content in 484 individual tree rings formed in the periods 770-780 and 990-1000 CE. Distinct 14C excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the precise dating of 44 tree-ring records from five continents. We also identify a meridional decline of 11-year mean atmospheric radiocarbon concentrations across both hemispheres. Corroborated by historical eye-witness accounts of red auroras, our results suggest a global exposure to strong solar proton radiation. To improve understanding of the return frequency and intensity of past cosmic events, which is particularly important for assessing the potential threat of space weather on our society, further annually resolved 14C measurements are needed.
Keyphrases
  • particulate matter
  • genome wide
  • risk assessment
  • high intensity
  • energy transfer
  • heat stress
  • climate change
  • radiation induced