John J. Clague, R. W. Mathewes; Early Holocene thermal maximum in western North America: New evidence from Castle Peak, British Columbia. Geology ; 17 (3): 277–280. doi: https://doi.org/10.1130/0091-7613(1989)017<0277:EHTMIW>2.3.CO;2
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Conifer logs and branches of early Holocene age are common on the surface and in sediments above timberline at Castle Peak in the southeastern Coast Mountains of British Columbia. A study of this wood and associated peat and colluvium has shown that local timberline from 9.1 to 8.2 ka was at least 60 m, and perhaps more than 130 m, higher than today. Mean growing-season temperature at Castle Peak during this period thus may have been 0.4-0.8°C warmer than at present. This is consistent with theoretical considerations based on Milankovitch forcing of climatic change and is supported by other paleoecological data from the southern Canadian Cordillera and adjacent northwestern United States. A generally warm climate may have persisted until about 5-6 ka, followed by late Holocene cooling.