Long-term temperature trends and tree growth in the Taymir region of northern Siberia

The northernmost conifers in the world are located well above the Arctic Ci rcle in the Taymir region of northern Siberia and have been recording the t hermal environment for centuries to millennia. The trees respond to tempera tures beyond the narrow season of actual cambial cell division by means of root growth, photosynthesis, lignification of cell walls, and other biochem ical processes. Data from annual tree-ring widths are used to reconstruct M ay-September mean temperatures for the past four centuries. These warm-seas on temperatures correlate with annual temperatures and indicate unusual war ming in the 20th century. However, there is a loss of thermal response in r ing widths since about 1970, Previously the warmer temperatures induced wid er rings. Most major warming and cooling trends are in agreement with other high-latitude temperature reconstructions based on tree-ring analyses with some regional differences in timing of cooling in the late 18th century an d of warming in the late 19th century. (C) 2000 University of Washington.