Hot, wild and wet
NEW ZEALAND’S WEATHER IN 2018
If you thought 2018 was rather warm, then you were right — it was New Zealand’s second warmest year on record.
It is part of an overall warming trend, which a leading climate scientist says is a “wake-up call” for politicians to act.
In its annual summary released yesterday, Niwa said 2018’s mean of 13.41C was 0.8C above its records since 1909, equalling 1998.
It fell only to our most searing year on record, 2016, 0.84C above average.
Last year also marked a new record for the warmest minimum temperatures, previously held by 2016.
Niwa principal scientist Chris Brandolino said 2018 was part of a larger warming trend, with four of our past six years in the top five hottest years on record.
Brandolino said January was the warmest month of any year on record, at 3.1C above average.
Many parts of the country recorded their warmest year on record, including, Kerikeri, Te Kuiti, Hastings, Levin and Kelburn in Wellington.
Brandolino said there were three key drivers of the warm temperatures.
The first was ocean temperatures, with New Zealand experiencing a “marine heat wave” in the early months of the year. Some parts of the sea hit temperatures 2C above average.
“New Zealand is an island nation, so where ocean temperatures go, they also go on land.”
New Zealand also experienced more subtropical airflow in 2018, with many lows to the west and highs to the east driving northeast winds.
The increase in greenhouse gases, surpassing 400 parts per million, was the third factor, providing a “long-term tailwind to temperatures”.
Climate scientist Dr Jim Salinger had last week predicted 2018 would be our hottest year on record, but was happy with Niwa’s conclusion.
“We used slightly different calculations, but we are all consistent in that we are in the hottest period on record.”
Niwa also found 2018 had the hottest minimum, or overnight, temperatures on record.
Salinger said this was a “wake-up call” for politicians to take action on climate change.
“It is very concerning and politicians are not yet doing anything about it.
“We recognised this was happening back in 1980, now it is starting to almost get too late.
“The young are calling for it, so let’s get the Zero Carbon Bill in. The evidence is out there.
“As we see further temperature rises we are going to see a lot of extinctions, people living around the coasts and in small island states will be affected by rising seas, and our oceans will become more acidic.”
New Zealand is already experiencing dramatic impacts.
Last summer’s “unprecedented” heatwave led to the largest ice melt from our Southern Alps glaciers in the last 57 years when 3.8 cubic kilometres, or 9 per cent of permanent snow, went down our rivers.
The high temperatures drove very early sauvignon blanc wine-grape maturation in Marlborough, and major species disruption occurred in marine ecosystems with snapper being caught in Fiordland.
Salinger said the 2018 summary mimicked global trends, with surface temperatures over the past four years the warmest on record. Niwa’s seasonal climate outlook forecasts the next three months being above average too.
Salinger said this was consistent with predictions from the United Kingdom Met Office that 2019 would be close to a record due to global heating and the added effect of the El Nino in the tropical Pacific.
“The Met Office forecasts the global average temperature increase for 2019 to be between 0.98C and 1.22C, with a central estimate of 1.10C, above the preindustrial average period from 1850-1900.
“Since 1850, 2016 is the warmest year on record with a central estimate of 1.15C above the same baseline.”
Along with the heat there were several extreme weather events in New Zealand in 2018.
In a typical year one ex-tropical cyclone would come within 150km of New Zealand. In 2018, three ex-tropical cyclones impacted New Zealand in Fehi, Gita and Hola.
Gita, which struck over February 20-21, brought significant rainfall, leading to slips and road washouts.
In southeast Kaiko¯ ura, 202mm of rain fell in 30 hours — 28 per cent of its annual rainfall.
The major event for Auckland occurred over April 10-11, with extreme winds causing major power outages.
MetService meteorologist Lisa Murray said it was a very busy year for them, issuing many weather warnings.
“It was the wettest February on record for Nelson and Blenheim.
“The wind storm in Auckland [caused] the largest power cut in New Zealand’s history”.