That data over this near four-year period indicated that monthly temperatures across the country are either average or above-average.
The last time monthly temperatures dipped below average was January 2017, Niwa principal scientist Chris Brandolino said when releasing its climate summary for 2020.
Last year was NZ’s seventh warmest year on record.
“Six of the eight warmest years on record have occurred since 2013. This is consistent with climate change,” he said.
“We have always had events that happen naturally, that make things warmer than usual, but with climate change in the background, it accelerates that.”
Brandolino says what was concerning was that temperatures had increased by about a degree over the past 100 years.
“What we have seen this year (2020) – climate change has a role in that,” he said.
Globally, temperatures were warmer with 88% of the globe having above-average temperatures in 2020.
Six of the 12 months in 2020 had above-average temperatures, with the rest of the months having “near-average” temperatures.
Brandolino says warmer than usual ocean temperatures, the La Nina weather pattern, high air pressure and climate change all contributed to the hot temperatures.
Victoria University of Wellington climate scientist Professor James Renwick says the warming trend is clear in this country as it is around the world.
“Even though we do not see each year being successively warmer than the last, the warm years are piling up. A below-normal year now would be truly exceptional,” Renwick said.
He says the pattern of a dry north and a wet southwest, with strong westerly winds that characterised the drought is one that is likely to see more of in future as the climate continues to change.
The year was characterised as a year of record-breaking extreme weather.
After the effects of smoke from Australian bushfires in January last year dissipated, NZ experienced severe drought that would be one of the key themes of 2020, Brandolino said.
Niwa’s NZ drought index showed the dryness expanded and intensified across the country.
“In February the MPI classified Northland, Waikato and the Auckland regions as a medium-scale adverse event. In March this was upgraded to a large-scale adverse event,” he said.
That classification extended across much of the country.
Last year was New Zealand’s seventh warmest year on record. Photo: Supplied/NIWA
The dryness was underpinned by a record dry spells. These are classified by Niwa as days where there is 15 days or more with less than 1mm of rain on any given day.
In Blenheim, there was a dry spell that lasted for 64 consecutive days, a record for that town.
Auckland also had a record dry spell, which spilled over into water restrictions that lasted most of the year.
The warmest winter on record resulted in a lack of snow in the South Island for most of the season.
It was not dry everywhere. Last February flooding in Southland led to a state of emergency being declared and similar flooding in July in Northland led to 65 homes being evacuated.
Napier also had its second wettest day on record when 242mm of rain fell on November 9.
Rounding off the year of extreme weather was the hail storm on Boxing Day which affected South Island growers hard.
Auckland’s Western Springs and Mangere monitoring sites and Hamilton’s Ruakura site had its driest year since records began. In Hamilton those records went back to 1905.
“There were no regions that had near-record or record wetness,” he said.
Gisborne had the country’s highest temperature for 2020 at 38.2 on January 31, the fifth highest January temperature on record.
Looking ahead to the first quarter of 2021, Brandolino says there should be above-average temperatures and “lumpy” rainfall, which is characterised by significant rain lasting for up to two days breaking up extended dry spells.
Further out, he says the expectation for the coming decades is for a warmer climate, an increased rise in sea levels and more extreme rainfall.
