1. J. Overpeck is at the National Oceanographic and Atmospheric Administration (NOAA)–National Geophysical Data Center (NGDC) Paleoclimatology Program, 325 Broadway, Boulder, CO 80303, USA, and Institute of Arctic and Alpine Research (INSTAAR), University of Colorado, Boulder, CO 80309, USA. K. Hughen, A. Jennings, J. Moore, and A. Wolfe are at INSTAAR, University of Colorado, Boulder, CO 80309, USA. D. Hardy, R. Bradley, and S. Smith are in the Department of Geosciences, University of Massachusetts,...