2020 likely to be NZ's seventh warmest year

Auckland's biggest drought in 25 years coincided with an early-January orange haze created by Australia's devastating bushfires. Photo / Greg Bowker Visuals

This year is shaping up to be the seventh warmest New Zealand has ever recorded - continuing a clear trend driven by climate change.

It would mean that five of the country's top hottest years have all played out since 2013.

New Zealand's official temperature record, the Seven Station Series, is currently showing the average temperature to be 0.7C above average for 2020.

"To rank in the top five, we'd need an extremely warm December but while the forecast is looking warm, it might be a bit of a stretch," Niwa forecaster Ben Noll said.

A variable January and cooler March was what would most likely keep 2020 out of the top five, he said.

Today, the World Meteorological Organisation also announced that 2020 is set to be one of the three warmest years on record, with the average global temperature expected to be 1.2C above the 1850-1900 pre-industrial level.

"Another consideration is the very low soil moisture levels experienced earlier this year, with the lack of moisture in the ground making for better radiational cooling conditions at night," Noll said.

"Sea surface temperatures were above average in the New Zealand region so far in 2020 but slightly cooler than what was experienced over the same period in 2019."

Noll added that it had now been 46 consecutive months since New Zealand's nationwide average temperature was below average.

That comes as New Zealand this week formally declared a climate change emergency, with the Government pledging to make itself carbon-neutral by 2025.

A much wider picture of New Zealand's transforming climate has also been provided by a new study involving prominent Kiwi climate scientists, professors Jim Salinger and James Renwick.

Source / Niwa

Their analysis compared land temperatures recorded around the country between 1871 and 2019 with surrounding ocean surface data, finding our wider region has warmed by about 0.66C over that time.

Much of the heat has come over recent years, on the back of global warming.

The paper found our coolest years had all played out before 1933, and the hottest since 1998.

Between 1870 and 1895, temperatures were running at about 0.4C below the 1981-2010 average, then, in the early 1900s, dropped even further to 0.8C below that baseline.

Temperatures were also noticeably colder in the early 1930s, and then 0.4C below the average in the 1940s, and generally close to normal over the 1950s, 1970s and 1980s.

While they dropped again to around 0.5C below normal in early 1990s - partly because of the Mt Pinatubo volcanic eruption - they increased rapidly to 0.1C above normal, before averaging 0.4C above normal throughout the 2010s.

When this trend came in tandem with natural drivers that had historically made for balmier conditions, New Zealand saw extremely warm years.

A case in point was our hottest year on record - 2016 - which coincided with a pressure set-up that drove more northerlies and northwesterlies across the country.

Globally, greenhouse gas emissions are expected to keep rising - meaning rising, acidifying oceans and more weather events like heavy storms, drought and heatwaves.

At the current rate, the global average temperature is likely to cross the threshold of 1.5C above the pre-industrial level within the next 10 to 20 years.

And a rise of 3C by the end of this century is projected, even if all the current emissions reduction commitments and goals are met by the international community.