Two independent calibrated and verified climate reconstructions from ecologically contrasting tree-ring sites in the southern Colorado Plateau, U.S.A. reveal decadal-scale climatic trends during the past two millennia. Combining precisely dated annual mean-maximum temperature and October through July precipitation reconstructions yields an unparalleled record of climatic variability. The approach allows for the identification of thirty extreme wet periods and thirty-five extreme dry periods in the 1,425-year precipitation reconstruction and 30 extreme cool periods and 26 extreme warm periods in 2,262-year temperature reconstruction. In addition, the reconstructions were integrated to identify intervals when conditions were extreme in both climatic variables (cool/dry, cool/wet, warm/dry, warm/wet). Noteworthy in the reconstructions are the post-1976 warm/wet period, unprecedented in the 1,425-year record both in amplitude and duration, anomalous and prolonged late 20th century warmth, that while never exceeded, was nearly equaled in magnitude for brief intervals in the past, and substantial decadal-scale variability within the Medieval Warm Period and Little Ice Age intervals.
Bibliographical noteFunding Information:
The research necessary for this paper was supported by The Laboratory of Tree-Ring Research at The University of Arizona, National Science Foundation grant NSF-ATM 0213962 from the Earth System History Program, Desert Archaeology Inc. of Tucson Arizona, and the Arizona Department of Transportation. Logistical help was received from the United States Forest Service and Arizona Snowbowl. Help with fieldwork was received from Rex Adams, Jim Parks, Chris McPhee, Ian Parker, and Alison McDonald. Jim Parks and Angelica Clemens helped with laboratory analyses. The discussion benefited from the expertise of Julio L. Betancourt, Malcolm K. Hughes, Thomas W. Swetnam, Jeffrey S. Dean, V. A. S. McCord, Gary Funkhouser, anonymous reviewers, and many other individuals within the paleoclimatic community.