'Wake-up call' on climate change

Massive waves at St Clair Beach, Dunedin, may become a more common sight as the sea level rises....
Massive waves at St Clair Beach, Dunedin, may become a more common sight as the sea level rises. Photo by Stephen Jaquiery.
While Otago and Southland's agricultural sector could benefit from higher rainfall and warmer winters, the region's coastal environments will be at risk from greater erosion and storm events, Niwa climate scientist Dr Andrew Tait says.

Dr Tait, along with AgResearch scientist Dr Paul Newton and New Zealand Agricultural Greenhouse Gas Research Centre scientist Dr Andy Reisinger, were the lead authors of a chapter on New Zealand and Australia in the Intergovernmental Panel on Climate Change's Fifth Assessment Working Group 2 report released in Japan yesterday.

''It's a wake-up call.''

The report highlighted where signs of climate change impacting on the environment were being seen and predicted what the impacts were going to be as the climate continued to be affected by increasing concentrations of CO2 and other greenhouse gases in the atmosphere, he said.

Temperatures were predicted to increase by 2degC, depending on what inroads into reducing greenhouse gases were made.

Drought was expected to increase in frequency, even in Southland and Otago, and flooding was predicted to have a serious impact in some places as big storm events increased in frequency.

''The big ones will be even bigger. A 1-in-50-year could become a 1-in-20-year time frame by the end of the century.''

This would create a real risk to coastal infrastructure and create a need for communities to be well equipped if bigger floods come downstream, Dr Tait said.

Sea level rise of 0.5m to 1m was predicted, again depending on the reduction of greenhouse gas emissions, and if those reductions were not made the rise might be greater.

As a result, a lot more thought needed to be put in, not just at a local government level, at how coastal infrastructure and the country's ecosystems were going to be protected, he said.

At present, the Government provided guidance on climate issues while local government was charged with policy and planning decisions.

University of Otago geography department senior lecturer Dr Daniel Kingston said the report's predictions of increases in the strength of the prevailing westerly winds would mean inland and southern areas of Otago would see an increase in rain, primarily in winter and spring, and mostly in South Otago and inland towards the Southern Alps.

The expected changes would be good and bad for the region, such as reduced winter heating needs, but increased fire risk in summer, he said.

''The temperature-driven decrease in snow/increase in rainfall will be beneficial for hydropower generation in the short term, but the longer-term decrease in meltwater from snow and glaciers would increase vulnerability.

''Reduced winter snow will also mean more a greater reliance on snow-making machines for the ski industry.''

While higher temperatures in Otago would better suit conditions for pine forest growth, it would also be good for pine disease and pests, he said.

Otago Regional Council engineering, hazards and science director Gavin Palmer said the council had been including climate change considerations into its work for many years.

''This reinforces the need for such things. With this information, we'll review what we are doing and have planned.''

The regional council was working with the Dunedin City Council on its district plan review to ensure inclusion of hazard information.

Also as part of its regional policy statement review it was working with other councils in Otago to ensure climate change information was considered.

''We are taking it seriously.''

It was also including climate change considerations in upgrades of its flood protection infrastructure such as its recently commissioned Waipori pumping station.



The findings

• Rising snow lines, more frequent hot extremes, less frequent cold extremes and increasing extreme rainfall.

• Annual average rainfall expected to decrease in the northeast South Island and northern and eastern North Island, to increase in other parts of New Zealand.

• Regional sea level rise likely to exceed the historical rate (1971-2010)

• Rainfall changes projected to lead to increased run-off in the west and south of the South Island and reduced run-off in the northeast of the South Island, and the east and north of the North Island.

• Annual flows of eastward flowing rivers with headwaters in the Southern Alps projected to increase in response to higher alpine rainfall.

• Flood risk projected to increase in many regions due to more intense extreme rainfall caused by a warmer, wetter atmosphere.

• 50-year and 100-year flood peaks for rivers in many parts of the country will increase, with a corresponding decrease in return periods for specific flood levels.

• Flood risk near river mouths will be exacerbated by storm surge

• Very high and extreme fire weather in many, in particular eastern and northern, parts of New Zealand will increase

• Fire season length will be extended in many already high-risk areas, reducing opportunities for controlled burning.


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