Lack of cold temperatures is driving recent high-summer warming in the southern Rocky Mountains.

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Bibliographic Details
Title: Lack of cold temperatures is driving recent high-summer warming in the southern Rocky Mountains.
Authors: Torbenson, M. C. A.1,2 (AUTHOR) mtorbens@uni-mainz.de, Martinez del Castillo, E.1 (AUTHOR), Reinig, F.1 (AUTHOR), Stahle, D. W.3 (AUTHOR), King, K. E.4 (AUTHOR), Maxwell, J. T.5 (AUTHOR), Harley, G. L.6 (AUTHOR), Ziaco, E.1 (AUTHOR), Esper, J.1,2 (AUTHOR)
Source: International Journal of Biometeorology. Jun2025, Vol. 69 Issue 6, p1475-1486. 12p.
Subject Terms: *Earth sciences, *Cold (Temperature), *Tree growth, *Physical geography, *Wood, *Tree-rings
Abstract: We present a 483-year-long tree-ring chronology from a high-elevation Engelmann spruce stand in central Colorado. Over 800,000 density measurements produce a maximum latewood density (MXD) record, which together with tree-ring widths, is used to assess the climatic influences on radial tree growth. Variability in MXD is strongly related to local and regional August maximum temperatures (Tmax) for 127 years of overlapping instrumental climate data. A single-predictor reconstruction based on the MXD record explains > 50% of the variance in regional August Tmax is presented and considered robust for the period 1662–2021. The estimates of past temperature variability display phases of continuous cold conditions that are beyond the range of the instrumental record, including the 1830s. Our results further indicate that August Tmax have been higher since the early 1990s than for any other 30-year period in the past 350 years. This recent increase occurs on top of multi-centennial warming, and appears to be driven mainly by less frequent cold summers rather than an increase in warm extremes. [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
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Abstract:We present a 483-year-long tree-ring chronology from a high-elevation Engelmann spruce stand in central Colorado. Over 800,000 density measurements produce a maximum latewood density (MXD) record, which together with tree-ring widths, is used to assess the climatic influences on radial tree growth. Variability in MXD is strongly related to local and regional August maximum temperatures (Tmax) for 127 years of overlapping instrumental climate data. A single-predictor reconstruction based on the MXD record explains > 50% of the variance in regional August Tmax is presented and considered robust for the period 1662–2021. The estimates of past temperature variability display phases of continuous cold conditions that are beyond the range of the instrumental record, including the 1830s. Our results further indicate that August Tmax have been higher since the early 1990s than for any other 30-year period in the past 350 years. This recent increase occurs on top of multi-centennial warming, and appears to be driven mainly by less frequent cold summers rather than an increase in warm extremes. [ABSTRACT FROM AUTHOR]
ISSN:00207128
DOI:10.1007/s00484-025-02904-9