Climate change report highlights city's at risk areas

A report, commissioned by the Dunedin City Council, identifying the areas of Dunedin most vulnerable to climate change has been released today.

The report, by University of Otago Emeritus Professor of Geography Professor Blair Fitzharris, outlines the expected current best estimates of climate change for Dunedin. These include temperature changes of up to 1.1degC by 2040, and up to 2.5degC by 2090; rainfall increase of up to 5% by 2040 and 15% by 2090, and sea level rises of up to 1.6m by 2090.

Prof Fitzharris explains that factors controlling the climate of Dunedin will largely stay the same as at present, but as projected global warming takes hold, there will be a slow increase in sea surface temperatures, an increase in the strength of the westerlies wind band over Southern New Zealand, and more frequent and vigorous frontal systems.

“The weather will remain changeable, but it will gradually become warmer. After the 2040s, what is currently regarded as a warm year will have become the norm. Risks from frost and low level snow storms will markedly decrease.”

Increased evaporation from higher temperatures is expected to be offset by higher rainfall, so drought incidence will remain largely unchanged for most of the city.

Rainfall events will become about 20% more intense, leading to higher storm runoff but lower river levels between events. Larger floods are expected, leaving low-lying areas near river mouths and estuaries vulnerable.

The main areas of Dunedin at risk from projected climate change are low-lying, densely populated, urban areas, especially South Dunedin; coasts and their communities; major transport infrastructure including Dunedin Airport; and natural ecosytems.

Five hotspot areas of the city especially vulnerable to change are: the South Dunedin urban area, including the St Clair and St Kilda shoreline; the harbour-side shoreline, including the entrance to Otago Harbour; the lower Taieri Plain, especially Dunedin Airport; populated estuaries along the Pacific Coast; and conservation lands of upland regions.

Prof Fitzharris has recommended the DCC should develop policy responses that focus on adaptation to the expected changes, rather than measures to reduce the amount of greenhouse gases produced. “This is because major long-term planning and infrastructure problems will result from the expected very large and ongoing impacts.

“While Council should encourage mitigation, less attention should be given to this issue, except where it leads to energy efficiencies or protects the city’s tourist image” concludes Prof Fitzharris.

However, should “shrewd adaptation measures” be realised, there were some sectors of the city that could benefit from climate change. These include agriculture and forestry, due to longer and better growing seasons, less frost and increased rainfall. Energy use in the city could also fall due to reduced demand in winter, and water resources could benefit from increased stream flows.