The big warm: NZ heading for warmest-ever winter

by Gareth on August 26, 2013

If you think it’s been a warm winter in New Zealand, you’re right. NZ is rapidly approaching the end of a record-breaking winter — the warmest for at least 150 years1. Calculations by Auckland climate scientist Jim Salinger show that NZ’s average temperature for June/July/August is running at 9.5ºC, a remarkable 1.2 deg C above the 1971-2000 average, and comfortably ahead of 1998′s old record of 9.3ºC. Commenting on the numbers, Salinger notes the absence of cold snaps in recent months:

The door to cold spells from the Southern Oceans — apart from a brief surge in June — has been well and truly closed this winter. September-like temperatures have been occurring throughout August, giving the country its warmest winter and August ever.

The long term warming signal is clear, he says:

The clearest climate warming signal is seen in winter, where temperatures are now 1.1 deg C warmer than they were around 1870. The warming trends have been very consistent, especially since the 1950s, when frosts days have decreased dramatically across the country.

I can certainly vouch for the absence of frost. At Limestone Hills, we recorded 19 frost days in 2011 and 23 in 20122, but only 6 so far this year. Evidence of winter warmth can be seen in gardens around the country. The asparagus spear pictured above first poked its head out of our soil two weeks ago, and is now being joined by half a dozen more — at least a month earlier than normal for North Canterbury.

To unpick just why this winter’s been so warm, I asked VUW climate scientist Jim Renwick to look back at the atmospheric circulation set-up in the New Zealand region. Here’s his (lightly edited) analysis:

For the winter as whole:

Pressures were anomalously high to the east of New Zealand, weakened westerlies. Unusually low pressures down over the far south central Pacific. 1000-500hPa mean temperatures were 1-1.5 deg C above normal over New Zealand. The NIWA outlook for winter temperature was near-perfect!

For August:

Anomalously high pressures southeast of New Zealand, linked to a negative Southern Annular Mode (SAM) signature. Northerly flow anomalies over New Zealand. 1000-500hPa mean temperatures around 2 deg C above normal over New Zealand. You can see a warm ‘tongue’ extending from subtropics to Antarctic, at the longitudes of New Zealand.

When I contacted Jim R for his take on the winter, I noted that the Antarctic sea ice — which in recent years has tended to “bulge” north towards New Zealand — is reduced to our south, but unusually far north in the Pacific to the west of South America. He found that a strong northerly flow anomaly over Ross Sea ( giving anomalously warm air there), southerly over Amundsen/Bellingshausen (anomalously cold there), helped to produce that sea ice pattern.

Jim R’s conclusion:

So, it has been a warm winter, brought about by persistent anticyclones east of New Zealand, a combination of the negative SAM (at times) and the tendency for zonal wave 3 ridges3 to sit near the Date Line. Lots of northerly wind flow anomalies over New Zealand, associated with persistently warmer than normal air.

Across the Tasman, Australia has also had an unusually warm winter, and 2013 is shaping up to be the country’s hottest year on record. The NZ record, with updated numbers, will be officially confirmed by NIWA in early September.

Listen to Jim S discussing the record on RNZ National’s Morning Report:

Warmest winter on record

  1. Reliable temperature records in NZ date back to the 1860s. []
  2. For the full year. Frost days are any day where the temp falls below zero, and are unusual (1 – 2 a year) after August. []
  3. Aka Rossby waves. Zonal waves can be considered as persistent “wiggles” in the jetstream that affect the way that surface weather systems track around the world. Jim will be giving a talk on ZW3 at AGU in December. []

{ 16 comments… read them below or add one }

Bob Bingham August 26, 2013 at 2:35 pm

Jim Salinger is an astute scientist and an excellent reporter on climate change. I wish our politicians would take him and the rest of the NZ scientific community seriously. If we are lucky New Zealand will not suffer as badly as the larger continental masses and the North. I have just watched this talk by Peter Sinclair who went with Jason Box on the Dark Snow project. http://www.youtube.com/watch?v=9euZ6q4bEKs&feature=share
The Arctic might seem a long way away but we are all part of one World.

Kiwipoet August 28, 2013 at 9:04 am

As someone commented, even the cold snaps are getting warmer. Warmer could well mean dryer for some parts of NZ. We had four months of no rain here on Waiheke Island last summer and we could be heading in the same direction this year.

The media reported it, but downplayed it. National Radio gave Salinger a couple of minutes on morning report. Labour leadership change got 20 min. Will ful blindness is a painful thing to witness.

Thomas August 28, 2013 at 5:04 pm

The effects of a lesser snow cover will also be significant for the annual water flow balance to lower lying areas.
Besides, if the trend continues, the Whakapa ski field may find it economically difficult to remain profitable too. (not that that matters on a scale of things but as a Canary in the coal mine…)

nigelj August 30, 2013 at 11:29 am

People dont really undertand concepts like the greenhouse effect, or all the other climate change theory and projections, but they do understand a warm winter. Or unusual droughts in America etc.

They will eventually connect this to sea level rise and reach a level of understanding of the scale of the issue. Another couple of years of unusual weather will end the debate for all but the fanatic sceptics.

noelfuller August 31, 2013 at 9:00 am

During my last year at seconary school, late 50s, both my physics teacher and my chemistry teacher endeavoured to explain the “greenhouse effect”. However, they were dealing with people who had no idea what they were really talking about, nor did the teachers try to explain its significance. Yet a friend of mine who is about 10 years younger remembers doing at school experiments with CO2 to show this effect. I find this remarkable and wonder if anyone here did such experiments at school and whether they reached any idea of the significance at the time?

Thomas August 31, 2013 at 9:32 am

I am a science teacher and used this video as a demonstration:
https://www.youtube.com/watch?v=SeYfl45X1wo

noelfuller August 31, 2013 at 8:04 pm

An effective demonstration. I then noticed quite a few other video demos of the heat trapping character of CO2.

Thomas September 1, 2013 at 11:21 am

The demonstration uses a band filter looking only at the transmissions in the absorption bands of CO2. Unfortunately you can not do this in the classroom without special equipment as the visible light and even the IR light outside the absorption bands hides this effect to the naked eye.

Macro August 31, 2013 at 2:26 pm

The Greenhouse effect wasn’t included in my secondary schooling – but as a Science teacher in the early 70′s I remember that it was included in the 4th Form Curriculum The CO2 experiment was included in the “Science Makes Sense” series for a start. In the late 70′s early 80′s I was working on the Naval Staff In Def HQ Wellington and living in Silverstream just down the road from Jim Salinger who was just completing his Thesis at the time, and many times we traveled on the train together to and from Wellington. I can clearly recall my asking – is there warming with the increasing concentration of CO2? I can also clearly recall his reply “It’s too early to tell”. Those who claim that Climate Scientists have preconceived opinions have no idea.

noelfuller August 31, 2013 at 8:32 pm

When I was teaching I formulated a view that it takes about 50 years for a new idea to work its way down to primary school level but here we are talking about secondary school levels and if there was any teaching in the 60s on the heat trapping properties of CO2 then that lag was 100 years. Even fewer have caught on to Fourier’s hypothesis, the lag being much longer.

Tony August 30, 2013 at 12:21 pm

On the issue of what we should be doing about it, Peter Wadhams makes the claim that we should be pursuing thorium. This will no doubt delight Andy S, but does Wadhams know something we don’t? Has the state of play changed such that thorium is now a viable alternative?

Fiesty Weta September 2, 2013 at 4:56 pm

Just calculated final New Zealand temperatures for August and winter…they come in as:

Winter +1.13 C warmest on record back to late 1860s

August +1.75 warmest on record back to late 1860s

Macro September 3, 2013 at 3:57 pm

And you just tell that to Ken Ring and he’ll never believe you! ;)

Thomas September 3, 2013 at 5:33 pm

Ken Ring needs no thermometer. He has seen snow this year, so anybody who says it was warm must be wrong as any school child knows that its cold when it snows…. ;-)

Rob Taylor September 4, 2013 at 1:14 pm

Poor, persecuted Ken Ring! How has it come to this?

Once a valued member of the NZ Skeptics, he now requires retinue of bodyguards and $5,000 in advance just to appear at their annual conference…

http://conference.skeptics.org.nz/blogs/kenring

Thomas September 5, 2013 at 8:45 pm

We are taught that there are no coincidences in science.” (Ken Ring, writing to the NZ Skeptics, see the link above that Rob posted.

Well, I knew that Ken missed out somewhere in his science education. And I think he has just let it slip! In fact this is the hinge pin of it all, isn’t it?

Ken, in case you are listening, coincidences are in fact abundant in our natural world. It is a key fallacy of the human mind to see causation in all sorts of correlations when in fact no cause – effect connection exists at all.

This is indeed the reason why so many people are beholden by ‘magical thinking’, homeopathic ‘cures’, astrological predictions, superstitions and so on.

It is one of the key tasks of scientists worthy their degrees, to weed through the mountains of chaff of coincidental events to reveal those significant ones, that are evidence of patterns, natural laws and cause and effect. And this dear Ken, is the one lesson you should have taken to heart a very long while ago and much of the ridicule you had to endure, could have been avoided completely.

Many people before you have been taken for a wild ride by their beliefs in cause and effect relationships for observed correlations. The confirmation bias from a strong ego plus a ready market for so many people who want to believe and pay for it too, make for a great environment in which all sorts of conjecture can be monetized. Your endeavor is a prime example of just this.

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