Don't mention Hunga Tonga

For months the country has felt as if it’s under a state of siege – not from a hostile foreign power, but from extreme weather. 

This week, the north of the country has been pummelled again by torrential rain, gale-force winds and high seas. RNZ reported this morning that more heavy rain warnings had been issued for the west coast of the North Island and the top of the South. 

But please, whatever you do, don’t mention Hunga Tonga.

Constant weather warnings have created a pervasive sense of anxiety. Night after night, the TV weather maps show heavy rain. I’m surprised that the graphics people even bother to redo them.

We’ve become familiar with scary colour codes denoting storms of varying severity. Meteorologists whom no one had previously heard of have been thrust into national prominence in the same way that epidemiologists became household names - celebrities, almost - during the Covid crisis. 

But the experts don’t say anything about Hunga Tonga, and quite rightly. We wouldn't want people to get the wrong idea.

In some areas, Taranaki being the latest, residents have been advised to have emergency grab bags prepared in case they have to be evacuated suddenly. In Nelson last night, the city council opened emergency accommodation as a precaution.

In Hawke’s Bay, Tairawhiti, Coromandel and West Auckland, traumatised farmers, orchardists, grape growers and home owners are still cleaning up after Cyclone Hale, Cyclone Gabrielle and the Auckland Anniversary Weekend floods. In parts of Hawke’s Bay, people are still digging themselves out from under several metres of silt.  But please don’t make the mistake of thinking this has anything to do with Hunga Tonga.

Vital highways remain closed by storm damage. SH2 between Napier and Wairoa, closed for three months, is scheduled to reopen on May 14 once a Bailey bridge has been completed on the devastated Waikare Gorge section. Repairs to SH25A on the Coromandel Peninsula may take until next year. But it would be pure mischief to implicate Hunga Tonga.

The Wairarapa, where I live, has largely escaped the worst of the mayhem, although floodwaters inundated the Tinui School, on the road to Castlepoint, and forced its closure. But even here, we’re lamenting a summer that never was. One rural contractor, in business since 1988, said it was the wettest season he’d experienced. Crops went unharvested because the rain was almost constant.

Masterton got through summer without water restrictions, which is almost unheard of. Lawns that would normally be mown every few weeks, and then only to keep the weeds down, just kept growing. The glorious hot, dry spells that we’ve come to expect since moving here 20 years ago just didn’t happen.

The statistics tell the story. In January, 182mm of rain fell at Masterton Airport compared with the historical average of 83mm. In February we got 159mm compared with the average of 25mm.

And when it wasn’t raining, it was threatening to rain. It was a summer of gloom. NIWA figures show that Masterton had 536 hours of bright sunshine during summer compared with the average of 649. That may not sound like a huge difference, but ask any family camping on the coast how much fun they had this summer. Not bloody much, they’ll tell you. But Hunga Tonga? Nah.

By now you’re probably muttering, “Hunga what?” and wondering what the hell I’m on about.

Hunga Tonga-Hunga Ha’apai is the underwater volcano that erupted near Tonga in January last year. I wrote about it here.

To recap a couple of key points from that blog post, Hunga Tonga was the most powerful eruption so far this century. According to NIWA, it was the biggest atmospheric explosion recorded in more than 100 years, measuring nearly 6 on the volcanic explosivity index – roughly equivalent to that of Krakatoa. The eruption created a volcanic plume that reached 58km into the mesosphere.

An article in the scientific journal Communications Earth and Environment – one of many devoted to the event – noted that major volcanic eruptions are well-known drivers of climate change and said the magnitude of the Hunga Tonga explosion ranked it among the most remarkable climatic events in the modern observation era. Researchers calculated that it resulted in a 13% increase in global stratospheric water mass and a fivefold increase in stratospheric aerosol load – the highest in three decades.

One study estimated the amount of water displaced as 58,000 Olympic-sized swimming pools, or about 10 percent of the entire water content of the stratosphere. That’s a helluva lot of water and it has to go somewhere. Communications Earth and Environment said the eruption had “potential long-lasting repercussions for stratospheric composition and climate”.

Similarly, Atmosphere magazine devoted a special issue to the eruption, calling it an epic event that would have a continuing effect on the climate, both locally [that probably includes us] and globally.

It seems reasonable to conclude that an eruption of that scale might at the very least be a factor in the freakish weather patterns of the past few months. Yet I can’t help suspecting that the eruption of Hunga Tonga is the climate event none of the New Zealand experts want to talk about, possibly because it cuts across the official narrative that the extreme weather of the past few months is all due to climate change.

In a New Zealand Herald article published two months ago, New Zealand meteorologists seemed to go out of their way to play down the Hunga Tonga factor. While acknowledging that eruptions can have climatic impacts, they attributed our wayward summer weather (and now autumn as well) to other causes. James Renwick said much of the excess moisture from Hunga Tonga would have been rained out within weeks. He and Jim Salinger posited that La Niña and something called the Southern Annular Mode were far more important. The other big factor, of course, was background climate change. Nothing new to see here, folks.

Obviously I can’t contradict them. They’re experts and I’m not. But can we rely on the likes of Renwick and Salinger being rigorously objective? I’d like to say yes, but both have nailed their colours to the climate change mast and the subject is so politicised that we can be excused for having doubts. Science is not immune to ideological contamination, as we learned from the shameful gang-up that followed the Listener letter about matauranga Maori.

Setting aside all the arguments about whether climate change is human-induced, and to what extent (if at all) we can mitigate it by riding bikes, buying Teslas, planting trees and punishing farmers, I think most people can accept that the climate is changing. Even my own amateur observations suggest it’s happening. One admittedly crude measurement is the frequency with which the Remutaka Hill road is closed by slips. When we moved from Wellington in 2003, such events were infrequent. Now they happen regularly. That can only be the result of the ground being saturated and destabilised by constant heavy rain. The frosts, too, are fewer and less severe.

But what’s happened lately feels different. Gabrielle was New Zealand’s worst weather event this century. The Treasury puts the likely combined cost of the cyclone and the Anniversary Weekend storm at $9-$14 billion.

Climate change is surely a gradually evolving trend, and that doesn’t gel with what New Zealand has experienced this year. The recent extreme weather events have been freakishly violent and abrupt. They feel like outliers – striking departures from the norm – rather than the predictable continuation of a long-term pattern. If I'm wrong, such events are the new normal and we face an unimaginably dismal future.

Just by suggesting this, I probably risk being labelled as a conspiracy theorist from the alt-Right and put on the watch list of the Disinformation Project (which, incidentally, has so far failed to respond to my requests for information about who funds it – a novel approach for activists who like to promote themselves as champions of transparency). But where climate change is concerned, as in all issues where ideology intrudes, I’m inclined to follow the advice of my late colleague Frank Haden: doubt everything with gusto.