Large-scale changes in observed daily maximum and minimum temperatures: Creation and analysis of a new gridded data set

[1] A gridded land-only data set representing near-surface observations of daily maximum and minimum temperatures (HadGHCND) has been created to allow analysis of recent changes in climate extremes and for the evaluation of climate model simulations. Using a global data set of quality-controlled station observations compiled by the U. S. National Climatic Data Center ( NCDC), daily anomalies were created relative to the 1961 - 1990 reference period for each contributing station. An angular distance weighting technique was used to interpolate these observed anomalies onto a 2.5 degrees latitude by 3.75 degrees longitude grid over the period from January 1946 to December 2000. We have used the data set to examine regional trends in time-varying percentiles. Data over consecutive 5 year periods were used to calculate percentiles which allow us to see how the distributions of daily maximum and minimum temperature have changed over time. Changes during the winter and spring periods are larger than in the other seasons, particularly with respect to increasing temperatures at the lower end of the maximum and minimum temperature distributions. Regional differences suggest that it is not possible to infer distributional changes from changes in the mean alone.