New Zealand winters are a month shorter than they were 80 years ago, due to rising temperatures around the globe, which will influence the life cycle of plants and animals, scientists from the National Institute of Water and Atmospheric Research (NIWA) said on Wednesday.
Winter is conventionally regarded as occurring between June 1 and Aug. 31 in the Southern Hemisphere -- a total of 92 days. If defined using temperature, however, winter lengths will vary from year to year, according to principal climate scientist Brett Mullan.
For example, in 2016, winter was essentially confined to July and August because June was unusually warm and August unusually cold, but 2017 was more the reverse, with August unusually warm, Mullan said in a statement.
Mullan has examined official temperature records from NIWA's Seven Station Series which began in 1909. The series uses climate data from seven geographically representative locations around the country, he said.
The number of frosts in New Zealand was also reducing in many locations, especially higher altitude inland regions of the country, he added.
The statistics are mirroring trends worldwide, Mullan said, adding the United States also reported a shortening of winter, with the first frost of the year arriving more than a month later than it did 100 years ago.
"This is a consequence of rising temperatures around the globe, and such trends in colder temperatures and frosts will influence the life cycle of plants and animals," the scientist said.