Climate change: 2020 NZ's seventh-warmest year on record

2020 was New Zealand's seventh-hottest year on record, a new report has revealed.

The Annual Climate Summary, released on Tuesday by the National Institute of Water and Atmospheric Research (NIWA), says the average temperature in 2020 was 13.24C - 0.63C above the average recorded between 1981 and 2010.

Six months of the year had temperatures well above the norm, six about average and none below average. It's now been 47 months since New Zealand experienced a month of below average temperatures (January 2017). 

Six of the past eight years have been the hottest since records began in 1909, NIWA said, with two outliers from the late 1990s making the list. 

A graph provided by the forecaster shows just how frequent above-average temperatures are occurring - covering 1909 to the present day, it starts off blue with the odd anomalous light red stripe, before turning deep red in the last decade as the warming effect of climate change starts to bite.

NIWA temperature years
Photo credit: NIWA

The warmest place overall was Leigh, a small community north of Auckland, which averaged 16.9C. Whangarei and Kaitaia, also in Northland, came in second on 16.6C.

2020 began with a cold snap which quickly gave way to a heatwave, with several locations setting record highs - Gisborne on January 31 recorded the hottest temperature of the year, a sweltering 38.2C (the country's fifth-hottest January temperature ever). 

The second-warmest temperatures were recorded in Napier (37.4C) and Wairoa (37.3C), both on February 2.

Warm and dry conditions arrived in February and March as the country went into lockdown, causing water supply shortages in places like Auckland and Northland. Some regions had less than 10 percent of the rain they'd normally get. 

Blenheim went 64 days without significant rainfall between December 2019 and February 2021. Auckland managed 47 days between January and February, the longest on record. 

February was particularly warm, more than 1.2C above average. 

There was rain in the deep south however, with floods in Fiordland, Otago and Southland, and a cold snap hit the eastern coast of the South Island.

Anomalous temperatures over the year.
Anomalous temperatures over the year. Photo credit: NIWA

The big dry continued into April, again affecting most of the country except the far south.

"Several locations in Wairarapa, coastal Marlborough and coastal North Canterbury received less than 5mm of rain for the entire month," NIWA said. 

Rain came in winter, but temperatures remained relatively warm - snow levels at 10-year lows and ski areas struggling to attract business, even as Kiwis unable to travel overseas looked to their own backyard for tourism opportunities. It was the fifth-warmest June on record, and sixth-warmest August. Timaru reached 25.1C on August 30, the fourth-warmest winter temperature anywhere in the country on record. 

The coldest snap came in September, helping out ski fields and sending daytime temperatures to zero in Southland and Otago. The year's coldest temperature was recorded on June 14 at Middlemarch in Otago - a chilly -12.3C. 

The heat came back in October and November, fanning wildfires and water shortages in some parts of the country and dousing others in heavy rain. Napier had 242mm of rain on November 9 - the second-wettest day on record. It ended the month with six times as much rain as usual.

Waikato had 200 percent as much rain as normal, as did Hawke's Bay, Taranaki, Wellington, Nelson and Tasman. The situation in the south flipped, with below-normal rainfall in much of Southland, Fiordland, and the southern half of the West Coast.

Everywhere but Stewart Island dried up in December as summer arrived. 

Temperature anomalies across the world.
Temperature anomalies across the world. Photo credit: NIWA

Whakatane racked up the most sunny hours - 2704 - followed by Nelson (2632) and Marlborough (2603). 

"Of the six main centres in 2020, Auckland was the warmest, Dunedin was the coolest, Wellington was the wettest, Christchurch was the driest, Tauranga was the sunniest and Dunedin was the least sunny," said NIWA.

New Zealand isn't alone in experiencing a warm year - 88 percent of the globe measured temperatures above the historical average, NIWA said.