New Zealand is being warned to prepare for floods, droughts and fire over the next century as a result of climate change and global warming.
The outlook comes from the Intergovernmental Panel on Climate Change (IPCC) whose key findings on impacts were released yesterday in a worldwide series of regional briefings.
The IPCC was formed in 1988 to provide scientific advice on climate change and assesses current knowledge in six yearly reports.
Dr David Wratt, a review editor and leader of Niwa's national climate centre, said in Auckland that the IPCC was an impartial body and "not trying to prove anything", allowing the science to speak for itself.
It involved over 1200 scientific authors and 2500 expert reviewers from more than 130 countries, and in a report this year concluded that global warming was indisputable and "very likely" to be man-made.
Dr Wratt said there was no doubt the world was seeing the effects of climate change caused by human activity since 1750, especially the burning of fossil fuels.
Changes observed in New Zealand since 1950 included a warming in mean temperature of 0.4 degC, a decrease in cold nights and frosts by 10 to 20 days per year, a sea level rise of about 70mm, and a loss of at least a quarter of alpine ice mass.
The report predicted that by 2080 there could be up to a 3.5 degC rise in average temperatures and increased rainfall except in the eastern North Island and the northern South Island.
Dr Wratt said New Zealand was more resilient to climate change than many other countries as it was surrounded by oceans but was nonetheless vulnerable to serious events such as major floods.
The IPCC report identified a need to plan for climate changes but said little research had been done.
There were major implications for New Zealand communities including the costs of injury and trauma due to increased storm intensity and higher extreme temperatures, degraded beaches due to sea levels rising and larger storm surges.
There were risks to flora and fauna from climate change in alpine zones and freshwater habitats.
Heat-related deaths were likely to double from 14 to 28 people aged over 65 each year.
There could be an increase in agricultural production up to the year 2050 in parts of the country because of higher carbon dioxide concentrations, longer growing seasons and less frost but that would be offset by increased droughts and fire risks in other areas.
Dr Wratt said efforts could be made to avoid the risks of climate change such as restricting development in flood prone areas or building larger stormwater drains.
But the report identified barriers including ongoing scepticism, a lack of integrated assessments of climate change impacts and weak linkages between levels of government to deal with it.
The report had found water security, natural ecosystems, and coastal communities were the three sectors most vulnerable to climate change in New Zealand and identified hotspots.
The coast in Northland and the Bay of Plenty was at particular risk from sea-level rises and storms by 2050, the eastern lowland regions were at risk from increased drought, and the Southern Alps at risk from glacial shrinkage and loss of biodiversity.
As a result of reduced precipitation and increased evaporation, water security problems were projected to intensify by 2030 in Northland and some eastern regions.
Niwa scientist Dr Jim Salinger, lead author of the chapter in the report referring to Australia and New Zealand, said the potential impacts of climate change were likely to be substantial without further adaptation.
Dr Salinger said New Zealand had the capacity to cope with small amounts of climate change due to its well-developed economy and strong scientific and technical capabilities.
"But there are considerable constraints to implementation and there will be major challenges from changes in extreme events and larger amounts of changes in climate."