Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data

Abstract

A number of reconstructions of millennial-scale climate variability have been carried out in order to understand patterns of natural climate variability, on decade to century timescales, and the role of anthropogenic forcing. These reconstructions have mainly used tree-ring data and other data sets of annual to decadal resolution. Lake and ocean sediments have a lower time resolution, but provide climate information at multicentennial timescales that may not be captured by tree-ring data. Here we reconstruct Northern Hemisphere temperatures for the past 2,000 years by combining low-resolution proxies with tree-ring data, using a wavelet transform technique to achieve timescale-dependent processing of the data. Our reconstruction shows larger multicentennial variability than most previous multi-proxy reconstructions, but agrees well with temperatures reconstructed from borehole measurements and with temperatures obtained with a general circulation model. According to our reconstruction, high temperatures--similar to those observed in the twentieth century before 1990--occurred around ad 1000 to 1100, and minimum temperatures that are about 0.7 K below the average of 1961-90 occurred around ad 1600. This large natural variability in the past suggests an important role of natural multicentennial variability that is likely to continue.

Reconstruction of early spring temperature for central Japan from the tree‐ring widths of Hinoki cypress and its verification by other proxy records

“…However, some similarities should be noted at an interdecadal resolution. Suppressed temperatures are found for the periods I to V from the comparison with the Northern Hemispheric temperature reconstruction [Esper et al, 2002], whereas those by Moberg et al [2005] and Huang [2004] support only our cold periods II and IV.…”

The Medieval Climate Anomaly and Little Ice Age in Chesapeake Bay and the North Atlantic Ocean

“…10) show that warm CB SSTs between 600 and 1000 CE (Fig. 10a) overlap with the latter part of what is sometimes called the cool "Dark Ages" in Europe, predating the classical Medieval Warm Period seen in atmospheric temperature curves of Moberg et al (2005) and Mann et al (2008) (Fig. 10c).…”

“…This composite curve, referred to as RD-2209, covers the last 2200 years and has been incorporated into several northern hemisphere surface temperature reconstructions covering the last 2000 years (e.g. Mann and Jones, 2003;Moberg et al, 2005;Mann et al, 2008). However, RD-2209 is a composite of four cores, and one (PTXT-2) that covers the critical Little Ice Age comes from shallower water and a different location than other cores.…”

“…9a). This composite record is compared with temperature reconstructions from the Cariaco Basin (Black et al, 2004), the Laurentian slope upper North Atlantic Deep Water (NADW) (Marchitto and deMenocal, 2003), off northern Iceland (Sicre et al, 2008), the VØring Plateau (Andersson et al, 2003), and a northern hemisphere composite temperature curve (Moberg et al, 2005) (Fig. 9b-f).…”

“…2), as well as basin-wide (Marchitto and deMenocal, 2003). (d) Northern Hemisphere composite surface temperature (Moberg et al, 2005). (e) Alkenone biomarker SST record north of Iceland (Sicre et al, 2008, red line 5-point smooth).…”