by K. Richard, Mar 4, 2024 in NoTricksZone
The warmest 50-year period in northeastern China occurred from 1844-1893.
“Compared with single years, in general, high or low temperatures that persist for many years will more significantly affect the growth of trees [30]. When we defined years with T12-1 ≥ −10.73 °C (Mean + 1σ) and T12-1 ≤ −12.61 °C (Mean − 1σ) as extreme warm years and cold years, respectively, the reconstruction for the period of 1787–2005 contained 31 cold years and 36 warm years (Table 4). The extreme cold/warm events lasting for three or more consecutive years were discovered in 1965–1967 and 1976–1978/1791–1798, 1844–1849 and 1889–1891. An 11-year smoothing average of the reconstructed T12-1 series was performed to reveal multi-year and interdecadal variations and to detect the several prolonged cold and warm periods (Figure 5d). After smoothing with an 11-yr moving average, cold periods occurred in 1822–1830 (mean T12-1 = −12.7 °C) and 1957–1970 (mean T12-1 = −12.7 °C), while a warm period occurred in 1787–1793 (mean T12-1 = −10.4 °C) (Figure 5d). Rapid and sustained cooling was observed in the reconstructed series in the years 1790–1826 (T12-1 range −10.3 °C to −12.8 °C, mean = −12.0 °C) and 1939–1969 (T12-1 range −11.6 °C to −12.7 °C, mean = −12.1 °C), where the rates of cooling were about 0.067 °C/year and 0.035 °C/year, respectively (Figure 5d). The two cooling events may be due to the decrease in solar activity [48,49,50]. Using a 50-year time scale, the highest temperature occurring during 1787–2005 was from 1844 to 1893 (T12-1 range −12.79 °C to −9.41 °C, mean = −11.15 °C), similar results were also obtained by Zhu et al. and Jiang et al., while the lowest temperature was from 1940–1993 (T12-1 range −13.57 °C to −10.26 °C, mean = −12.13 °C) (Figure 5d) [33].”
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