SURFACE-TEMPERATURE TRENDS AND VARIATIONS IN NEW-ZEALAND AND THE SURROUNDING OCEAN, 1871-1993

We compare homogenized series of maximum, minimum, and mean air temper ature averaged over New Zealand, measured between 1871 and 1993, with rigorously quality controlled marine temperature data measured over th e surrounding ocean surface. The marine data are those of sea-surface temperature (SST) and air temperature measured at night (NMAT) on boar d ship, both corrected for time-varying instrumental biases. There is mostly very good agreement between the variations in the three data se ts on time-scales down to a season. Some disagreements are related to short periods of sparsely observed marine data, particularly during th e World Wars. Differences also exist between trends in the maximum and minimum New Zealand temperatures (NZT), particularly in winter. In ad dition, interannual variations in winter NZT tend not to track those o f nearby marine temperatures quite as well as happens in other seasons . Although it is not the main purpose of the paper to discuss the caus es of NZT change, New Zealand temperature is known to be influenced by the EI Nino-Southern Oscillation (ENSO) phenomena. Tropical East Paci fic SST variations are strongly related to ENSO and so are well correl ated with NZT on time-scales of a few years to near a decade. We discu ss these relationships, and also associations with Southern Hemisphere SST. We conclude that annual NZT and NMAT over the nearby ocean surfa ce have both warmed by about 0-7 degrees C since the beginning of the century, with a slightly smaller increase in SST. This confirms previo us work on the magnitude of the warming of New Zealand climate this ce ntury. Warming in NMAT and NZT in each season varies in a similar way, with consistently slightly smaller increases in SST. We also conclude that the UK Meteorological Office seasonal historical marine temperat ure data set appears to be generally of very good quality in the New Z ealand region.