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After an extended summer of record high temperatures and unusually heavy storms the evidence is mounting of the dangers we are running by stressing the planet's climate systems. I used to joke to my friends that we would win the argument about humanity's responsibility for climate changes because "we have the planet on our side". I think I was right, but it is not so funny now that the planet is increasingly demonstrating the extent of its power to disrupt our lives. More and more people are seriously asking "what can we do?".
It turns out that Dunedin is at the cutting edge in New Zealand of both of these trends: being exposed more than most to the challenges of a changing climate; and also taking the challenge seriously. Late January saw a packed St David's lecture theatre listen to Climate Change Minister James Shaw and our own Mayor Dave Cull report on their experiences at the latest global climate change conference in Bonn. And in February, the council adopted a target for the city to be carbon-neutral by 2050, excluding methane "for now". Also in February, the Blueskin Bay Resilient Communities Trust with the support of the Deep South National Science Challenge ran a series of workshops on the ways that climate change is likely to affect Dunedin, and what must happen if we are to manage our way through the very considerable disruptions it will bring.
As South Dunedin already knows, parts of the city can expect to experience a slow but inexorable rise in average sea levels. Waikouaiti and the Taieri Plain, including Mosgiel, will also be increasingly vulnerable. But the real damage will come not from this slow and steady creep but from the increasing frequency and severity of extreme events of the kind we began to see this summer. For example, a rise of 0.8m in average sea level will mean that what we now think of as a 1-in-100 year high tide will be exceeded in more than 90% of all high tides. In other words, what used to happen every 100 years would happen 50 times a month.
A warmer planet is also a wetter planet, but that general rule does not apply evenly. NIWA estimates that the north and east of the North Island will become drier over this century, as will the Southern Alps. But Dunedin is predicted to experience an increase in rainfall of about 15%. And again it is not the average but the extremes that will do the damage. With increasing frequency, tropical cyclones like February's Gita will bring high winds and extreme rainfall further south as the planet warms.
The rising frequency of extreme tides, floods and storms will increase the stress on Dunedin's infrastructures for water, sewage and roading. If ignored, we must anticipate that pipes will be corroded by sea water, storm water systems will be infiltrated from sewage system overflows, gravity-fed systems will become inoperative in low-lying areas, water supplies will be compromised, and slips will increasingly disrupt and damage roads, housing and other buildings. For New Zealand as a whole, the asset value of storm and waste water systems is estimated to be more than $20 billion, so upgrading infrastructure to meet the new realities will not come cheaply. But at least we understand that these assets deliver benefit to us all and that we all have a stake in getting the work done.
More challenging are the costs to private owners of homes and businesses affected by rising seas. A Ministry for the Environment report estimates that more than 43,000 homes in New Zealand are within 1.5m of average spring high tides, nearly 9000 within 50cm. And recall again that it is tidal extremes beyond the average that will do the damage. It is estimated that about 22,000 people, or about 20% of Dunedin's population, are vulnerable to climate-induced coastal damage. To cover the additional costs, we can expect private insurance premiums to rise, excess limits to be raised, and in the toughest situations, properties to become uninsurable. To what extent will publicly-funded insurance step in to cover climate risk to private assets, in the way that EQC is charged with doing for earthquakes, and will that cover be adequate?
Mayor Dave Cull reports from the Bonn conference that it is cities around the world that are leading the charge in taking on these challenges. He also reports that we in New Zealand have been slow to take the dangers seriously. But as the city in New Zealand most at risk from rising sea levels, it is not surprising that Dunedin should now be facing up to the hard questions. The workshops run in February diagnosed the conditions necessary for the city to respond to these questions in a managed way, avoiding the chaos that great stress could otherwise bring. We would all need to understand and accept the need to change, and be willing to participate in shared efforts to transition to a carbon free future, navigating our way through differing interests and points of view. This will work best if we have ample opportunity to contribute to building a shared long-term vision or plan for the city.
It has been a wonderful summer. But we would be wise to also see it as a harbinger of greater changes to come. The good news is that our city has the courage to face up to these changes and may well find the will to create a city that will show how good life can be in a city without carbon.
Colin Campbell-Hunt is an emeritus professor at the CSAFE Centre for Sustainability, University of Otago. Each week in this column, one of a panel of writers addresses issues of sustainability.
• The next climate impacts adaptation public workshop is on Friday, March 16 in South Dunedin. You can find information here: http://climatesafehouse.nz.event