Climate scientist points to last year's warmth and temperatures expected for this year.
Last year was New Zealand's second warmest on record and more above-average temperatures are in store this year, says climate scientist Dr Jim Salinger.
The Auckland-based weather expert, author of the new book Living in a Warmer World, said warmer than average temperatures would continue long-term as the globe heats up.
Compiling data from 22 land stations and three islands, Dr Salinger found the New Zealand region's mean temperature for last year was 0.84C above the 1961-1990 long-term average of 12.17C.
It was the region's second warmest year since reliable records began in 1870, with mean temperatures well above average during March, July, August and November.
Record mean annual temperatures occurred in Masterton, Omarama, Timaru, Invercargill and the Chatham Islands, and mean temperatures during winter were 1.27C above the long-term average, the highest on record.
The New Zealand region had only two cooler than average years - 2004 and 2009 - in the past decade.
The 10-year mean temperature for 2004-2013 was 0.26C above average, the highest on record, Dr Salinger said.
His findings followed the Australian Bureau of Meteorology's announcement that the Australian area-averaged mean temperature last year was 1.2C above the long-term average - the highest since records began in 1910. Australians have begun the year in a heatwave with temperatures reaching the high-40s.
Early figures had also shown above average temperatures worldwide last year, according to the World Meteorological Organisation, which produces an estimated global mean temperature by drawing on data from three global climate datasets maintained in the United Kingdom and the United States.
Preliminary data from the organisation for between January and November indicated that the estimated global mean temperature for 2013 was 0.49C above the long-term average of 14C.
Dr Salinger said 2013 was the world's sixth-warmest year since global records began in 1880.
"No year since 1985 has recorded a below-average global mean temperature and nine of the ten warmest years have occurred in the past 12 years."
In New Zealand, he said the warmer than average year could be partly put down to a neutral El Nino-southern oscillation (ENSO) - meaning neither El Nino or La Nina patterns influenced our temperatures.
Meanwhile, interdecadal Pacific oscillation (IPO) - a cyclical change in the Pacific ocean-atmosphere system which affects New Zealand's climate - was negative, favouring more easterlies and northeasterlies at times with above average temperatures.
"At the same time sea surface temperatures were above average by around 1C, especially surrounding the South Island and to the east."
More ENSO-neutral conditions were expected to continue this year until at least winter, while negative IPO conditions were likely to last for the rest of the year.
"These conditions are presaged to bring above average temperatures of 0.2C to 0.6C above average for the New Zealand region."
The forecast painted a similar picture to that of the National Institute of Water and Atmosphere (Niwa) between December and next month.
Niwa gave a 40 per cent chance of temperatures being near average or above average in the north and east of the North Island and the east of the South Island, while above average temperatures were the most likely outcome in other regions.
Dr Salinger said New Zealand regional temperatures had warmed by 0.5 since 1950, and by more than 1C overall - a general trend expected to continue under climate change.
Figures from the UK Met Office predicted global average temperatures would remain between 0.28C and 0.59C above the 1971-2000 long-term average between the 2013 and 2017.