All but one MP voted last month for Zero Carbon legislation. That doesn't change the record of some powerful former MPs who flirted with denialism. Charlie Mitchell and Felippe Rodrigues review the decades of climate change debate in New Zealand's Parliament.

It was like any other day in Parliament. MPs were arguing about issues like gang numbers, social housing, and the low number of telephone connections in Christchurch.

Then the discussion briefly turned to something else, which – 40 years later – has a significance that was not apparent at the time.

It concerned the natural gas plant at Kapuni in Taranaki, which had gone into production that year. Fraser Colman, Labour MP for Petone, was concerned about the flaring of natural gas; in particular, its effect on the environment.

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​So he asked then Environment Minister, National's Venn Young, this question: "...Is the Minister aware of the growing scientific concern about rising CO2 levels and the potential for atmospheric warming, with consequential effects on forestry and the weather?"

It appeared to be the first reference to anthropogenic climate change in New Zealand's Parliament. Four decades later, climate change is regularly discussed in Parliament, but it took a long time to get there.

Stuff has analysed Hansard, the database containing Parliamentary records, to create a picture of climate change in Parliament. How and when it has been talked about, and which political parties and individual MPs have raised the issue the most.

Much like the global mean temperature, or the average sea-level, the frequency of Parliamentary debate around climate change has risen at escalating speed.

It was many years after Colman's early reference to "atmospheric warming" that climate change became a topic of serious, protracted debate.

The next MP to pick up the mantle was National's Simon Upton. On July 15, 1986, Upton – then an opposition MP – was debating the Environment Bill, sweeping legislation that established the Ministry for the Environment and the Parliamentary Commissioner for the Environment (an office that Upton, incidentally, now holds).

One of Upton's criticisms of the Bill was its lack of reference to international environmental issues. "During the next 50 years, environmental problems will not be confined to the country of origin of the problem or to single countries," he said.

He alluded to one of those problems - "global warming".

From then on, climate change was referenced in Parliament at least once a year.

Those early discussions were largely dominated by Geoffrey Palmer who, in the late 1980s, was Minister for the Environment before becoming Prime Minister. From 1987-1990, Palmer referred to "climate change" or "global warming" 44 times, far more than any other MP, and in the process became the first prime minister to refer to climate change in Parliament.

In 1990, he issued this stark warning: "There is no doubt that over the next decade the problem of coming to grips with climate change will be one of the most serious that the Government has to deal with."

It took much longer.

Parliamentary discussions about climate change sort along party lines, but not as strongly as might be expected.

We analysed every reference to climate change in Parliament since 2003, ending with the passage of the Zero Carbon Act in November 2019. We matched every reference to a person and a political party (earlier references were counted manually).

Of course, an MP can talk about climate change without explicitly saying "climate change". We chose certain phrases to serve as a proxy for a reference to climate change. They were: "climate change", "global warming", "carbon dioxide", "methane", "climate crisis", greenhouse gas", and "sea-level rise".

We found around 7500 mentions of those phrases since 2003, two-thirds of which were "climate change".

Our analysis showed Green Party MPs reference climate change the most, with around 2500 mentions collectively since 2003. They were far ahead of other parties: Labour and National were nearly even, with 2200 and 2150 references respectively. Rounding out the rest were NZ First, the Māori Party, ACT, United Future, and the Progressives, in that order.

What makes the Greens' dominance striking is its relative paucity of MPs. It had 24 members over that period who used the keywords at least 10 times, with an average of 103 references each.

It's significantly higher than any other party. On the same metric, the next is National (53), followed by Labour (46).

While Green MPs dominate climate change discussion, it is not a Green MP responsible for the most mentions of climate change in Parliament.

That would be National's Nick Smith, who has made 640 unique references to climate change since 2003. He is far ahead of any other MP - next is former Green co-leader Russel Norman with 403, followed by Labour's David Parker with 400.

This is partly because Smith is one of just a handful of MPs who was in Parliament for the entirety of this period. He was also active, both as opposition spokesman and Minister, during the period where climate change was discussed the most, during the transition between Labour and National-led Governments.

There have been three noteworthy spikes in climate change references. The first, in December 2008, resulted in 340 references, most of them on a single day, December 16.

On that day the newly elected National government was repealing two laws; one related to a phase-out of thermal power stations, and the other a law requiring fossil fuels to have some component of biofuel. Both were passed under urgency, meaning all readings of the Bill were held in succession.

That day was significant in another way. It contained the maiden statement for newly elected Labour MP Jacinda Ardern, who spoke in opposition to one of the repeal Bills, and said in her statement: "National told us we should be fast followers, but now all I see are the many, many losers — the future generations whom some people in this House do not yet believe they have a responsibility to. Well, I do."

The second, in November 2009, came with the passage of reforms to the Emissions Trading Scheme. The third - and the day in which climate change was discussed more than at any point in the preceding decade - was November 8, 2019, for the final reading of the Zero Carbon Bill.

A reference to climate change doesn't tell you whether the person speaking believes in it or not.

An analysis of the content of those references show, for the most part, MPs of all major parties accept the science of anthropogenic climate change, extending all the way back to the late 1980s.

There is one glaring exception - ACT. Many of its MPs over this period made explicit or implicit references to non-belief in the scientific consensus.

Most conspicuous was former leader Rodney Hide, who, in 2008, said: "I think I will be the only person speaking in this debate who has any qualifications in environmental science. It is not that that should count, but I think it is significant for what I am about to say — that is, that the entire climate change and global warming hypothesis is a hoax, that the data and the hypothesis do not hold together, that Al Gore is a phoney and a fraud on this issue, and that the emissions trading scheme is a worldwide scam and a swindle."

He was certainly not alone in his caucus.

Other ACT MPs who dismissed human influence on climate change were Gerrard Eckhoff ("Increasing evidence is being put forward by internationally renowned scientists — and I have articles flooding in constantly on that very subject — that says no to the global warming concept"); Don Brash ("To justify participation in the Kyoto Protocol we need to be convinced of three things, all of which are highly contentious. First, we need to be persuaded that global warming is actually taking place..."); Ken Shirley ("As we know, climate change is a highly debatable matter. There is a lot of spurious science around it"); Deborah Coddington ("This bill is all about sustainable development, and that is a nonsense phrase in itself. We have reached this point because of the myth about global warming and whether it will do any harm"); and John Boscawen ("I acknowledge that there is climate change, but since 2001 temperatures on this globe have been going down, so I ask why we would penalise working New Zealanders when we are not certain there is an impact.")

While such views were rarely seen in the major parties, a small number of their MPs have flirted with denialism.

Among them, most notably, is John Key, who as an MP in 2005 said: "The impact of the Kyoto Protocol, even if one believes in global warming — and I am somewhat suspicious of it — is that we will see billions and billions of dollars poured into fixing something that we are not even sure is a problem."

That suspicion did not remain long: In 2007, he was quoted saying "human-induced climate change is real and it's threatening the planet".

kevin stent SUNDAY STAR TIMES Don Brash and John Key, pictured when they were both senior National Party MPs in 2006. Both questioned the overwhelming scientific consensus about human-induced climate change.

In the early 2010s, there was a noticeable ebb in climate change discussions in Parliament, likely due in part to the Canterbury earthquakes as well as the lack of any signature climate change legislation.

That started to change in May 2016, with further changes to the ETS, and even more so in May 2019, with the introduction of the Zero Carbon Bill. The first reading of that Bill resulted in more discussion of climate change than any month since November 2009.

It was eclipsed once more in November 2019, when the Zero Carbon Bill became law.