QUANTILE SPLINE MODELS FOR GLOBAL TEMPERATURE-CHANGE

The Hansen and Lebedeff data set on global surface air temperature cha nge is reanalyzed using smoothing splines designed to estimate the con ditional quantile functions of global temperature over the last centur y. It is assumed only that the quantiles are smooth functions of time. The smoothness of the fitted quantile functions is determined by a da ta driven version of the Schwarz criterion. The estimates offer statis tical evidence of a break in the generally upward sloping trend of the temperature series during the period from 1940 to 1965, a finding ori ginally suggested by Hansen and Lebedeff (1987).