New Zealand has had its warmest and wettest winter on record, with one meteorologist describing it as “mother nature’s way of expressing she has a fever”.
For the three months to the end of August 2022, the average temperature was 9.8C, according to New Zealand’s National Institute of Water and Atmospheric Research (Niwa).
That figure was 1.4C above the 1981-2010 average from Niwa’s seven-station temperature series, which began in 1909, surpassing last year’s winter record of 1.3C.
It is the third consecutive year the temperature record has been broken and climate change was having a significant impact, said Ben Noll, a Niwa meteorologist.
“The warmth is here to stay,” he said. “We are not seeing anything at least in the next couple of seasons that will suggest we’re going to be seeing cooler than average temperatures.”
It was not just the winter season in which temperatures were consistently high, he said.
“We feel like a broken record … but this is mother nature’s way of expressing she has a fever – she is running a higher temperature and it is pretty concerning to see that, successively, season after season.”
This year’s winter was also the first on record where the temperature rise exceeded 1.2C for all three months of the season, relative to the long-term average.
Of the 10 warmest winters on record, six have occurred since 2013. This year, 50 locations experienced record temperatures and another 33 experienced near-record temperatures.
“The warmth was really overwhelming … it was certainly widespread in terms of the season as a whole,” said Nava Fedaeff, another Niwa forecaster.
Wairoa, on the east coast of the North Island, recorded the highest temperature of the winter, with 24.3C on 20 August, while the lowest was in Aoraki/Mount Cook on 17 July at -11.6C.
It was also the wettest winter since records began in 1971, which was “probably not a surprise to anyone”, Fedaeff said.
“We had extreme rainfall. There were really few places in the country that didn’t receive some of that rainfall.”
Noll added the atmospheric river that swept over the country was unusual for winter. It was the strongest on record for August and second strongest for winter since at least 1959.
“The characteristics of this event were more typical of what we expect in January, February or March,” he said.
A state of emergency was called in Nelson, Tasman, the West Coast and Marlborough after the torrential downpours, with Nelson in particular affected by severe flooding as the Maitai River burst its banks.
“The river flows well exceeded the previous record,” Noll said.
The record-breaking warmth did not stop at land-based temperatures, with sea surface temperatures also exceeding previous records after a third straight year of La Niña conditions.
Marine heatwave conditions in the eastern Tasman Sea and the Coral Sea not only contributed to warmer temperatures on land but also provided extra moisture to low-pressure systems approaching the country.
“You can really see how New Zealand’s weather … was connected to the tropics,” Noll said. “That resulted in atmospheric rivers and heavy rainfall throughout the season and some of that is [now] spilling over into the spring.”
