Northern Hemisphere temperature reconstruction during the last millennium using multiple annual proxies

Abstract

Previous studies have either exclusively used annual tree-ring data or have combined tree-ring series with other, lower temporal resolution proxy series. Both approaches can lead to significant uncertainties, as tree-rings may underestimate the amplitude of past temperature variations, and the validity of non-annual records cannot be clearly assessed. In this study, we assembled 45 published Northern Hemisphere (NH) temperature proxy records covering the past millennium, each of which satisfied 3 essential criteria: the series must be of annual resolution, span at least a thousand years, and represent an explicit temperature signal. Suitable climate archives included ice cores, varved lake sediments, tree-rings and speleothems. We reconstructed the average annual land temperature series for the NH over the last millennium by applying 3 different reconstruction techniques: (1) principal components (PC) plus second-order autoregressive model (AR2), (2) composite plus scale (CPS) and (3) regularized errors-in-variables approach (EIV). Our reconstruction is in excellent agreement with 6 climate model simulations (including the first 5 models derived from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) and an earth system model of intermediate complexity (LOVECLIM), showing similar temperatures at multidecadal timescales; however, all simulations appear to underestimate the temperature during the Medieval Warm Period (MWP). A comparison with other NH reconstructions shows that our results are consistent with earlier studies. These results indicate that well-validated annual proxy series should be used to minimize proxy-based artifacts, and that these proxy series contain sufficient information to reconstruct the low-frequency climate variability over the past millennium.

Toward a late Holocene glacial chronology for the eastern Nyainqêntanglha Range, southeastern Tibet

“…9. Compilation of dating results from this and selected other studies, and paleoclimate reconstructions: (A) oldest-tree moraine dating results, this study, vertical black lines show the calculated germination date, (B) 14 C dating result, this study, light gray bars indicate alternative interpretations of the result which are invalidated by morphological constraints, (C) oldest-tree moraine dating results younger than 1800 CE from selected other studies (see text), 1 Lhamcoka (Br€ auning and Lehmkuhl, 1996), 2 Lhamcoka (Br€ auning, 2006, 3 Gawalong, only terminal moraine crest positions (Zhu et al, 2013), 4 Midui, only terminal moraine crest positions , (D) temperature reconstruction for southeastern Tibet (Zhu et al, 2011; solid line is the 11 yr running mean), (E) reconstruction of summer precipitation anomalies from Reting (Grießinger et al, 2011; solid line is the 11 yr running mean), (F) multi-proxy reconstruction of northern hemisphere temperature anomalies (Shi et al, 2013; base period 1001e1960 CE, solid line is the 20 yr running mean), (G) reconstruction of volcanic forcing derived from ice core sulfate (Crowley and Unterman, 2013), (H) 14 C based reconstruction of solar modulation (Muscheler et al, 2007; solid line is the 20 yr running mean), (I) reconstructed sun activity (Steinhilber et al, 2009). quick succession of glacier advances around the Maunder minimum.…”

“…Temporal correlation of precipitation peaks and glacier advances is weak, implying that precipitation changes probably played a subordinate role in forcing the investigated glacier fluctuations. The temperature reconstructions for the northern hemisphere (Shi et al, 2013) and for the eastern Nyainqêntanglha by Zhu et al (2011) generally resemble the minima which are evident in records of solar forcing, e.g. reconstructions of solar modulation from 14 C data (Solanki et al, 2004;Muscheler et al, 2007) and solar activity from 10 Be data (Steinhilber et al, 2009).…”

Variability of summer humidity during the past 800 years on the eastern Tibetan Plateau inferred from δ<sup>18</sup>O of tree-ring cellulose

“…They address the effect of the moisture decrease on the reduction in the thermal gradient induced by uneven land-ocean temperature rise caused by aerosol and greenhouse gas loads. In fact, under rising northern hemispheric air temperatures (Shi et al, 2013), the air moisture load over sea is increased and the meridional moisture transport is contemporaneously hampered due to the black aerosol induced solar dimming effect (Sun et al, 2010). In addition, Zhao and Moore, 2006 attributed the moisture (Rayner et al, 2006).…”

Effects of solar forcing and North Atlantic oscillation on the climate of continental Scandinavia during the Holocene

“…Because of their precise and continuous timescale (varve chronology) and the response of their physical characteristics to environmental change, scientists have widely used varves in palaeoclimate reconstruction (e.g. Kaufman et al, 2009;Mann et al, 2009;Shi et al, 2013). Furthermore, being able to record the prominent features of changes with seasonal resolution, varved sediments are intriguing proxy records to understand and quantify the influence of external forcing on lacustrine sedimentation.…”