Variability and extremes of northern Scandinavian summer temperatures over the past two millennia

Jan Esper, Ulf Büntgen, Mauri Timonen, David C. Frank

Research output: Contribution to journalArticlepeer-review

58 Scopus citations

Abstract

Palaeoclimatic evidence revealed synchronous temperature variations among Northern Hemisphere regions over the past millennium. The range of these variations (in degrees Celsius) is, however, largely unknown. We here present a 2000-year summer temperature reconstruction from northern Scandinavia and compare this timeseries with existing proxy records to assess the range of reconstructed temperatures at a regional scale. The new reconstruction is based on 578 maximum latewood density profiles from living and sub-fossil Pinus sylvestris samples from northern Sweden and Finland. The record provides evidence for substantial warmth during Roman and Medieval times, larger in extent and longer in duration than 20th century warmth. The first century AD was the warmest 100-year period (+. 0.60.°C on average relative to the 1951-1980 mean) of the Common Era, more than 1. °C warmer than the coldest 14th century AD (-0.51. °C). The warmest and coldest reconstructed 30-year periods (AD 21-50 = +. 1.05. °C, and AD 1451-80 = - 1.19. °C) differ by more than 2. °C, and the range between the five warmest and coldest reconstructed summers in the context of the past 2000. years is estimated to exceed 5. °C. Comparison of the new timeseries with five existing tree-ring based reconstructions from northern Scandinavia revealed synchronized climate fluctuations but substantially different absolute temperatures. Level offset among the various reconstructions in extremely cold and warm years (up to 3. °C) and cold and warm 30-year periods (up to 1.5. °C) are in the order of the total temperature variance of each individual reconstruction over the past 1500 to 2000. years. These findings demonstrate our poor understanding of the absolute temperature variance in a region where high-resolution proxy coverage is denser than in any other area of the world.

Original languageEnglish (US)
Pages (from-to)1-9
Number of pages9
JournalGlobal and Planetary Change
Volume88-89
DOIs
StatePublished - May 2012
Externally publishedYes

Keywords

  • Climate variability
  • Common Era
  • Palaeoclimate
  • Scandinavia
  • Tree-rings

ASJC Scopus subject areas

  • Global and Planetary Change
  • Oceanography

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