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Saturday, April 13, 2024

New Zealand Faces a Future of Flood and Fire

New Zealand is grappling with two consecutive extreme weather events—massive flooding followed by a cyclone—that have claimed at least 12 lives and left hundreds of thousands of people without power. The high winds and waters of Cyclone Gabrielle have washed away coastal roads on the north island and left bridges splintered and broken. Landslides have covered tarmac with slick mud, and houses and streets across have been left under feet of water, only weeks after heavy rain also caused widespread floods. The country has declared a national state of emergency for just the third time in its history.

New Zealand’s climate change minister, James Shaw, wasted no time in pointing the finger at the root cause of the weather disasters, telling the New Zealand parliament: “This is climate change.” 

He may well be right, but the evidence from attribution studies is yet to come, says James Renwick, a climate scientist and professor at the Victoria University of Wellington. The cyclone itself isn’t unusual for New Zealand, as they regularly spin out of the tropics and get close enough to cause alarm, he says. “We’re in line for these things on a reasonably regular basis. Some of them are not that remarkable and some are absolutely catastrophic,” Renwick says. 

But our warming planet may have increased the ferocity of this cyclone because of warmer ocean waters, says Olaf Morgenstern, an atmospheric scientist at New Zealand’s National Institute of Water and Atmospheric Research. Hotter oceans mean that if a cyclone hits, “it will be stronger, it’ll contain more moisture, more energy and sustain its energy for longer,” he says.

New Zealand has also experienced marine heat waves linked to La Niña, a cyclical Pacific weather system, which has dominated the region for the past three years. These may have given the tropical cyclone a boost. “Because it was anomalously warm, it didn’t lose that much intensity—it was still pretty strong when it got here,” Morgenstern says. 

Record-breaking rainfall and flooding preceded the tropical cyclone and wreaked havoc on the north island in late January—this too seems likely to be connected to climate change. January broke a century-old record for Auckland’s wettest month, with 539 millimeters of rain recorded, half of that falling in a single day. That was truly unprecedented, Renwick says, but the likely impact of climate change on New Zealand will be more complex than simply more rain. 

The biggest influence on the regional climate are the winds that blow over the country from west to east. These deposit huge volumes of rain on the west coast of the south island in particular. Milford Sound, the famous fjord there that’s popular with tourists, is one of the wettest places on Earth, receiving a mean annual rainfall of 6.8 meters. The island’s mountains then force moisture out of the air as it passes over them, casting a rain shadow that leaves the east coast relatively dry. 

But introduce even subtle changes in the wind direction or the wind speed, and you  can end up with big changes in local climate, Renwick says. Climate modeling suggests those westerly winds are likely to get stronger. “Whether or not they lie over New Zealand so much is a tricky one to answer, because there’s a few moving parts of that story, but the broad picture is slightly stronger winds through time,” he says. An increase in strength is expected to deliver more rain to the west coast, and less to the east, resulting in hotter temperatures.

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The upshot is that New Zealand is now facing the prospect of bushfire seasons that could rival those of its notoriously flammable neighbor, Australia. “For the eastern parts of the country, the expectation is that the frequency of droughts will increase, maybe double through the rest of the century,” Renwick says. 

Another significant factor to account for is sea level rise, which, combined with flooding, could affect the majority of New Zealand’s residents, says Christine Kenney, a Māori sociologist and professor of disaster risk reduction at Massey University in Wellington. The biggest threat will be to built infrastructure. “We’ve got five airports that are going to be impacted, several thousand kilometers of roading, kilometers of railway,” Kenney says. “Two-thirds of New Zealanders live in areas prone to flooding and rising sea levels.” 

The cyclone has already cut numerous roads and bridges around the north island, leaving communities isolated. Even New Zealand’s largest international airport was submerged in the January floods. And that doesn’t begin to address the impact of these weather events on New Zealand’s farmers and producers. “New Zealand’s wine industry is going to be absolutely devastated, and this is just one storm,” Kenney says. 

When it comes to action on climate change, the independent Climate Action Tracker suggests New Zealand’s domestic emissions targets are “almost sufficient” for limiting the world to 2 degrees Celsius of warming. But the country’s actions and policies for actually hitting its targets are rated as “highly insufficient.” New Zealand’s single biggest source of greenhouse gas emissions is agriculture, with nearly 40 percent of emissions being methane from livestock.

But in the wake of these disasters, climate change mitigation and adaptation are likely to be major issues in the country’s election on October 14 this year. “The event that we have this week is unlikely to be forgotten very soon,” Morgenstern says. It will raise questions about how prepared New Zealand is for a future in which these sorts of extreme events will be potentially more commonplace.

“We need to be thinking really seriously now about not ‘building back better’ but ‘building back smarter,’ and where we build back,” Kenney says. While the notion of managed retreat from climate-exposed areas such as floodplains and coastlines is a deeply unpopular one, it’s not new. Certain areas of Christchurch were red-zoned after the 2011 earthquake, meaning that they were considered at too great a risk from subsequent seismic activity to be rebuilt. 

Kenney says there’s a lot of resistance to managed retreat from climate-exposed areas, but that doesn’t mean those conversations aren’t happening. “I think with what we’ve seen in the last week, those conversations at the governance and legislative level are going to take a very distinct turn.

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