The nationwide average temperature for the 2017-18 summer was 18.8 degrees Celsius, 0.3C above the previous 1934-35 record of 18.5C, and a significant 2.1C above the 1981-2010 averages.

Niwa principal forecasting scientist Chris Brandolino said the record-breaking summer was "not too surprising", however.

"Going back to the end of spring, late November, there were strong indications that this would be a summer that would be warmer than usual," he said.

"When we get these things happening, like a really warm ocean because of the marine heatwave - we've had really warm ocean temperatures going back to November - and when we have winds coming from the north, more than usual, you're going to get really warm weather. However, I think the difference-maker is we have climate change now. Our Earth is warmer than it was 20 years ago, 50 years ago, 100 years ago.

"When you have these conditions coming together like they did, no, it's not too surprising." 

The hot summer was characterised by mean sea level pressures being higher than normal, bringing more northerly and northeasterly winds than normal - consistent with La Niña conditions.

Natural climate variability explained the higher temperatures compared with 30 or 50 years ago, Brandolino said.

"The Earth is continuing to warm because of global greenhouse gas emissions."

View image on Twitter

NIWA Weather @NiwaWeather

2017-18: Kiwi Summer for the Record Books

Standout stats:

*The hottest summer on record by 0.3°C.
*The #marineheatwave had seas up to 6°C above average.
*Alexandra reached 38.7°C on 30 Jan, NZ's hottest Jan temp in 39 yrs.
*Above normal amount of ex-tropical cyclones (2).

8:58 PM - Mar 4, 2018

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CLIMATOLOGY OF THE TIME

The summer may have been a record-breaker, but the 1934-35 summer was more extreme in the context of its time.

Niwa has been recording temperatures nationwide since 1909, and Brandolino said that although the 2017-18 summer was hotter than that of 1934-35, the summer of 1934-45 was more of an anomaly because of the climatology of the time.

"In 1934-35, that summer was 2.7C above-average," he said.

So while that summer was 2.7C above-average, the 2017-18 summer was actually only 2.1C above the current 30-year average. 

When Niwa calculated temperature averages, it based it off a 30-year average. Currently, Niwa used the 1981-2010 average. 

"Every 10 years we readjust and form the new average," Brandolino said.

"Back in 1934-35, that 2.7C above-average temperature was relative to the New Zealand climatology at the beginning of the century. The baseline was a lower baseline."

NIWA Weather @NiwaWeather

2017-18: Kiwi Summer for the Record Books

Standout stats:

*The hottest summer on record by 0.3°C.
*The #marineheatwave had seas up to 6°C above average.
*Alexandra reached 38.7°C on 30 Jan, NZ's hottest Jan temp in 39 yrs.
*Above normal amount of ex-tropical cyclones (2). pic.twitter.com/dGbuNtdrjF

NIWA Weather @NiwaWeather

In terms of a difference from average, only 2017-18 and 1934-35 in the last 109 years have managed to exceed +1.25°C. #climate

Masterton experienced the largest mean temperature anomaly, or difference from average, anywhere in NZ this summer: +3.2°C. pic.twitter.com/zGUV14f0P1

9:15 PM - Mar 4, 2018

SO WHY ARE THE RECORDS SO FAR APART IF THE PLANET IS WARMING?

Even though the temperature trend has been an upward trend since Niwa started recording temperatures in 1909, Brandolino said that didn't mean the temperature averages would always be consistently rising.

"Even a bad marriage has a great weekend," he said.

Warm weather also meant different things for different people, he said. While some might be concerned about the effects of climate change, others might be excited about warmer summers.

"If you want to go on holiday and you like warm weather, then I suppose it's a good thing. But things like insects, pests, disease - there's a whole other line of implications from that."

Kiwifruit crops in the Bay of Plenty have been found to be at-risk because of warmer winter temperatures. A 2017 study by Niwa found growers in the region may soon be unable to grow green hayward kiwifruit because of warming temperatures. 

HIGHLIGHTS:

* A total of 54 NZ locations recorded their hottest summer on record, and 39 recorded their second-hottest and nine their third-hottest.
* Alexandra claimed the highest recorded temperature, reaching 38.7C on 30 January.
* The lowest temperature was 0.2C, recorded at Mt Cook and Tekapo on December 20.
* January was the hottest month on record, recording 20.3C, which was 3.1C higher than the 1981-2010 January average. 
* Of the six main centres, Auckland was the warmest, Dunedin the coldest and driest, Wellington the sunniest, and Hamilton the wettest and least sunny.

MEGAN GATTEY

March 5 2018

source: https://www.stuff.co.nz/

original story HERE

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