GEOGRAPHICAL-DISTRIBUTION OF CHANGES IN MAXIMUM AND MINIMUM TEMPERATURES

A dataset has been created containing monthly maximum and minimum temperatures over all of the world's land surface with available data. Procedures for assessing and correcting (where possible) station records for homogeneity are detailed, and a preliminary analysis is presented. Seasonal trends of maximum and minimum temperature, and diurnal range, are presented, revealing a marked decrease in diurnal temperature range in 1981-1990 compared with 1951-1980 over a large area of the world. Statistical tests used to find the significance of local and regional trends indicate that the decreases are most significant over Asia. The trends are tentatively related to changes in mean sea level pressure and rainfall. Time series analysis of maximum and minimum temperatures for the UK, ex-USSR, China, Turkey and the USA indicate that further improvements are needed in the homogenisation of maximum and minimum temperature data.