A 2000-yr reconstruction of air temperature in the Great Basin of the United States with specific reference to the Medieval Climatic Anomaly

Abstract

A sediment core representing the past two millennia was recovered from Stella Lake in the Snake Range of the central Great Basin in Nevada. The core was analyzed for sub-fossil chironomids and sediment organic content. A quantitative reconstruction of mean July air temperature (MJAT) was developed using a regional training set and a chironomid-based WA-PLS inference model (r2jack = 0.55, RMSEP = 0.9°C). The chironomid-based MJAT reconstruction suggests that the interval between AD 900 and AD 1300, corresponding to the Medieval Climate Anomaly (MCA), was characterized by MJAT elevated 1.0°C above the subsequent Little Ice Age (LIA), but likely not as warm as recent conditions. Comparison of the Stella Lake temperature reconstruction to previously published paleoclimate records from this region indicates that the temperature fluctuations inferred to have occurred at Stella Lake between AD 900 and AD 1300 correspond to regional records documenting hydroclimate variability during the MCA interval. The Stella Lake record provides evidence that elevated summer temperature contributed to the increased aridity that characterized the western United States during the MCA.

Global warming in the context of 2000 years of Australian alpine temperature and snow cover

“…A warming trend spanning the period from approximately 1130 CE to 1392 CE, overlaps with the widely reported timing of the MCA from Northern Hemisphere sites, although a clear synchronous onset of the MCA around the mid to late 900 s CE as seen in Northern Hemisphere records 44 , 45 is not evident (Fig. 3a,b ).…”

Millennial-scale increase in winter precipitation in the southern Rocky Mountains during the Common Era

“…The absence of a cooling during the LIA in the Park Range agrees with another pollen-based temperature reconstruction for the Southwest (Viau et al, 2012; Fig. 7C), chironomid-inferred temperatures from the Great Basin (Reinemann et al, 2014), and our understanding that the LIA is not expected to be globally synchronous (Matthews and Briffa, 2005). Based on fossil pollen records from across the continent, North America experienced an ~0.5°C increase in mean annual temperature during the MCA, followed by a decline to the lowest temperatures of the Common Era during the LIA (Trouet et al, 2013; Fig.…”

“…Some lake oxygen isotope records (Anderson et al, 2015) and macrofossil evidence of treeline changes (Jiménez-Moreno and Anderson, 2012) provide evidence of Common Era cooling. However, temperature reconstructions from western North America do not consistently show LIA cooling (Viau et al, 2012; Reinemann et al, 2014). Indeed, MCA warming and LIA cooling are not significant in continental-scale reconstructions given their uncertainty (Viau et al, 2006; Trouet et al, 2013), and the western United States subsets of the North American reconstruction show regional trends that differ from the continental mean patterns (Viau et al, 2012).…”

A chironomid-based reconstruction of late-Holocene climate and environmental change for southern Pacific Costa Rica

“…Sub-fossil chironomid analysis has proven to be valuable in developing quantitative temperature reconstructions for the late Quaternary (Porinchu and MacDonald, 2003; Walker, 2001; Walker and Cwynar, 2006). Chironomids are sensitive indicators of past temperature and offer great potential to provide independent estimates of regional climate conditions during intervals of transition (Axford et al, 2009; Engels et al, 2008; Levesque et al, 1997; Reinemann et al, 2014). The existence of strong, statistically significant correlations between chironomid assemblages and temperature (surface water and air) has facilitated the development of chironomid-based inference models from the high-, mid-, and low-latitudes (e.g.…”