NOAA/WDS Paleoclimatology - Northern Hemisphere Extra-Tropics 2,000yr Decadal Temperature Reconstruction

STUDY NOTES: Multi-proxy temperature reconstruction for the extra-tropical Northern Hemisphere (90-30°N) during the last two millennia based on 30 palaeotemperature proxy records with annual to multi-decadal resolution. Proxy types include historical documentary records, seafloor sediment records, lake sediment records, speleothem records, ice-core records, varved thickness sediment records, tree-ring width and maximum latewood density records. The reconstruction is presented as decadal anomalies in degrees C relative to the 1961–1990 reference period and provided with quantitative error bars.
ABSTRACT SUPPLIED BY ORIGINATOR: A new temperature reconstruction with decadal resolution, covering the last two millennia, is presented for the extratropical Northern Hemisphere (90-30°N), utilizing many palaeotemperature proxy records never previously included in any large-scale temperature reconstruction. The amplitude of the reconstructed temperature variability on centennial time-scales exceeds 0.6°C. This reconstruction is the first to show a distinct Roman Warm Period c. AD 1-300, reaching up to the 1961-1990 mean temperature level, followed by the Dark Age Cold Period c. AD 300-800. The Medieval Warm Period is seen c. AD 800–1300 and the Little Ice Age is clearly visible c. AD 1300-1900, followed by a rapid temperature increase in the twentieth century. The highest average temperatures in the reconstruction are encountered in the mid to late tenth century and the lowest in the late seventeenth century. Decadal mean temperatures seem to have reached or exceeded the 1961-1990 mean temperature level during substantial parts of the Roman Warm Period and the Medieval Warm Period. The temperature of the last two decades, however, is possibly higher than during any previous time in the past two millennia, although this is only seen in the instrumental temperature data and not in the multi-proxy reconstruction itself. Our temperature reconstruction agrees well with the reconstructions by Moberg et al. (2005) and Mann et al. (2008) with regard to the amplitude of the variability as well as the timing of warm and cold periods, except for the period c. AD 300-800, despite significant differences in both data coverage and methodology.