It said the last time the country recorded back-to-back record winters was in 1970 and 1971, but those years now stood at 18th and 13th respectively on the all-time list—which dates back to 1909.
“What was considered to be unusually warm at the time is no longer considered unusual,” NIWA meteorologist Nava Fedaeff said.
Fedaeff said natural weather patterns played a role in both record-setting periods but a key difference was the amount of carbon dioxide now polluting the atmosphere.
She said one measuring station near Wellington recorded a carbon dioxide concentration of 32 parts per million in the early 1970s but the level was now 412 parts per million, up almost 30 per cent.
“These similar winters, decades apart, show us that there are key natural ingredients to getting a warm winter, but adding climate change to the mix is like taking the same recipe and swapping plain flour for self-raising,” she said.
The country’s centre-left Prime Minister Jacinda Ardern declared a ‘climate emergency’ last year, saying urgent action was needed for the sake of future generations.
New Zealand has committed to becoming carbon neutral by 2050 and generating all of its energy from renewable sources by 2035.