Scoop has an Ethical Paywall
Work smarter with a Pro licence Learn More

Video | Business Headlines | Internet | Science | Scientific Ethics | Technology | Search

 

Winters much shorter than they once were, says NIWA

MEDIA RELEASE

WEDNESDAY, NOVEMBER 8, 2017


Winters much shorter than they once were, says NIWA

New Zealand winters are a month shorter than they were 80 years ago, NIWA scientists say.

Principal climate scientist Dr Brett 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.

Dr Mullan defined a winter’s day as one in which the daily average temperature was less than a selected threshold and then compared the number of days this occurred for two 30-year periods, the first from 1909 to 1938 and the second from 1987 to 2016.

Climate scientists consider 30 years to be the minimum amount of time to come up with a statistically meaningful long-term average.

The figures showed that, if a threshold of 9°C was chosen, then there was an average of 100 days per year between 1909 and 1938 when the temperature was less than 9°C, compared to only 70 days per year between 1987 and 2016. Winter has contracted about equally from both ends.

Winter is conventionally regarded as occurring between June 1 and August 31 in the Southern Hemisphere – a total of 92 days. If defined using temperature, however, winter lengths will vary from year to year. For example, in 2016 winter was essentially confined to July and August because June was unusually warm and August unusually cold. This year was more the reverse, with August unusually warm.

Advertisement - scroll to continue reading

Are you getting our free newsletter?

Subscribe to Scoop’s 'The Catch Up' our free weekly newsletter sent to your inbox every Monday with stories from across our network.

Dr Mullan said the number of frosts in New Zealand was also reducing in many locations, especially higher altitude inland regions of the country.

The statistics are mirroring trends worldwide. The US has 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”, said Dr Mullan.


Table of temperature thresholds
Number of days per year, on average, when daily temperatures in NIWA’s 7-station record are below a specified threshold

Threshold # days, 1909-1938 # days, 1987-2016
8.5 C 84 51
8.8 C 93 62
9.0 C 100 70
9.5 C 113 85

ends

© Scoop Media

Advertisement - scroll to continue reading
 
 
 
Business Headlines | Sci-Tech Headlines

 
GenPro: General Practices Begin Issuing Clause 14 Notices

GenPro has been copied into a rising number of Clause 14 notices issued since the NZNO lodged its Primary Practice Pay Equity Claim against General Practice employers in December 2023.More

SPADA: Screen Industry Unites For Streaming Platform Regulation & Intellectual Property Protections

In an unprecedented international collaboration, representatives of screen producing organisations from around the world have released a joint statement.More

 
 
 
 
 
 
 
 
 
 
 
 

Join Our Free Newsletter

Subscribe to Scoop’s 'The Catch Up' our free weekly newsletter sent to your inbox every Monday with stories from across our network.