New Zealand again just experienced one of its warmest summers on record, meteorologists will announce this week.

It will sit within our top five hottest summers in more than a century of records – the figures are being finalised by Niwa scientists – and more unusually warm weather is predicted for the months ahead.

The summer of 2018-19 might be best remembered for a week-long heatwave that set new maximum temperature records in Hamilton (32.9C) and Wellington (30.3C), or for baking the Nelson region, where a massive bushfire raged amid a 40-day dry spell.

Yet it followed what was the second-equal hottest year on record, and the hottest summer on record, which included the hottest month on record, and a record marine heatwave.

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On top of that, four of the past six years have been our warmest on the books.

Globally, the past five years have been the hottest of the post-industrial age.

While meteorologists are sensibly reluctant to blame any single weather event on climate change, the background picture is incontrovertibly one of warming.

That's raised a troubling question that researchers have just explored in a new study: are we at risk of normalising extreme weather at a time we should be most worried about it?

That research, just published by US scientists, indicates that people have short memories when it comes to what they consider "normal" weather.

On average, people base their idea of normal weather on what has happened in just the past two to eight years.

This disconnect with the historical climate record may obscure the public's perception of climate change, the researchers say.

FROGS IN THE POT

"There's a risk that we'll quickly normalise conditions we don't want to normalise," explained the study's lead author, Frances Moore, an assistant professor at the University of California at Davis.

"We are experiencing conditions that are historically extreme, but they might not feel particularly unusual if we tend to forget what happened more than about five years ago."

To reach their conclusions, the researchers quantified a timeless and universal pastime — talking about the weather — by analysing posts on Twitter.

They sampled 2.18 billion geolocated tweets created between March 2014 and November 2016 to determine what kind of temperatures generated the most posts about weather.

They found that people often tweet when temperatures are unusual for a particular place and time of year — a particularly warm March or unexpectedly freezing winter, for example.

However, if the same weather persisted year after year, it generated less comment on Twitter, indicating that people began to view it as normal in a relatively short amount of time.

This phenomenon, the authors noted, was a classic case of the boiling-frog metaphor.

A frog jumps into a pot of boiling hot water and immediately hops out.

If, instead, the frog in the pot is slowly warmed to a boiling temperature, it doesn't hop out and is eventually cooked.

Scientists observed the biggest snow melt observed in decades on the Southern Alps after 2017-18's record-hot summer. Photo / Dave Allen
Scientists observed the biggest snow melt observed in decades on the Southern Alps after 2017-18's record-hot summer. Photo / Dave Allen

While scientifically inaccurate, this metaphor has long been used as a cautionary tale warning against normalising the steadily changing conditions caused by climate change.

Sentiment analysis tools, which measure the positive or negative association of words, provided evidence for this "boiling-frog effect."

After repeat exposures to historically extreme temperatures, people tweeted less about the weather specifically, but they still expressed negative sentiments overall.

Particularly cold or hot conditions still seemed to make people unhappy and grumpy.

"We saw that extreme temperatures still make people miserable, but they stop talking about it," Moore said.

"This is a true boiling-frog effect. People seem to be getting used to changes they'd prefer to avoid.

"But just because they're not talking about it doesn't mean it's not making them worse off."

WHAT NEW ZEALANDERS THINK

Victoria University psychology professor Marc Wilson said although the study focused just on tweets out of the US, he assumed the picture wouldn't be much different here.

Studies now show New Zealanders are increasingly accepting climate change as happening and caused by man-made activities.

One recent survey suggested the majority of us now expect to see frequent and extreme storms, more droughts, inundated coastlines from sea level rise and extinctions of plant and animal species.

But concerningly, few New Zealanders thought the world would be able to do what's needed to escape the worst impacts.

"One question I'd have is whether the findings, as reported in this new paper, mean there's a problem," Wilson said.

"How does the pattern reported reflect in people's actual behaviour?

"By that, I mean that record breaking-related apathy is a problem if it means that people are less likely to act to change their behaviour in ways that are consistent with climate change mitigation strategies. That would be a problem."

And more so now than ever.

A United Nations report released last year, running to hundreds of pages of fresh scientific data and findings, showed the world was quickly running out of time to make a difference.

Stopping global warming from rising past 1.5C – as it was tracking to at some point between 2030 and 2052 – would spare up to 10 million people, not to mention tens of thousands of species, some of the worst impacts that a 2C scenario would.

Turning around the oil tanker that is the world's emissions would demand "unprecedented effort". We'd need to halve what we currently pump into the atmosphere - within just 12 years.

Climate scientist Professor Jim Salinger, however, doesn't think New Zealanders will be exposed to climate apathy as much as other countries.

"Everyone talks about the weather in New Zealand - because it is interesting and very changeable.

"And we are very open to extreme events such as extreme storms, floods, droughts and heatwaves.

"But as a country based on rural industries we are more strongly connected with the land than those large urban societies.

"Farmers keep good records so, as such, recognise the magnitude of any extreme. So, in my opinion we are less prone to such apathy."

But if a normalisation effect was taking place, how could that be countered?

"We need to remind people of exceptional or memorable events from the past, and point out that recent extremes are different," climate scientist Professor James Renwick says. Photo / File

Victoria University climate scientist Professor James Renwick said this was a tough question.

"Maybe we need to remind people of exceptional or memorable events from the past, and point out that recent extremes are different," he said.

"I think this would work for big cold events or heavy snow. I have noticed that the string of fairly mild winters we've had over several years makes us all vulnerable to thinking the world has ended when a genuine cold snap comes through."

Salinger thought it was useful to highlight the impacts that came with climate extremes.

"Last summer was a case in point: the unprecedented heatwave of 2017/18 saw Queensland groper, 3000km out of range in Northland, snapper in Fiordland and the greatest ice loss in the Southern Alps that had been measured, at least in the last six decades."

Wilson highlighted strategies that Dr David Holmes, director of the Climate Change Communication Research Hub at Australia's Monash University, shared at a New Zealand psychology society conference last year.

"One initiative that they championed was to contact a lot of the TV weather anchors around Australia and encourage them and their broadcasters to include trend information when they present the weather," he said.

"What this does is to provide people with an 'objective' indicator of any trends so that people aren't making a subjective comparison against a personal baseline.

"I think this would be a fantastic thing to have happen here in New Zealand."

A POLITICAL ISSUE

The other factor to consider was that, for some, climate change was a grand conspiracy somehow cooked up the overwhelming majority of the world's climate scientists and scientific academies.

In spite of the science, Wilson noted that climate change remained a political issue for many people.

"Research here, and elsewhere, shows that people have a vested interest in seeing themselves as rational and credible participants in what's going on around them, and this sometimes means we are very good at rationalising our experience to be consistent with what we already believe."

He referenced a well-known study led by New York University's Professor John Jost that involved asking people to estimate the ambient temperature during summer, as well as a little about their political beliefs.

It found that people who shared aspects of the psychological profile of a climate sceptic estimated that the weather was cooler than do those who agreed climate change was reality.

"Indeed, political identification is one of the strongest predictors of climate change belief both here and internationally."