One-in-100-year floods like those which recently submerged parts of Christchurch could be an annual event by the end of this century, scientists are warning.
The UN Intergovernmental Panel on Climate Change (IPCC) will release a report this afternoon that outlines the increasing effects of rising temperatures on New Zealand's agricultural industry and coastal communities.
Last year's report showed that the concentration of carbon dioxide and other greenhouse gases had increased to levels unprecedented in the last 800,000 years, and this one makes it clear New Zealand is underprepared for what lies ahead, says Victoria University Antarctic Research Centre director Prof Timothy Naish.
"This year's report makes it very clear that… the world is facing 2 to 4degC of global warming, so this report asks the question about how we're going to deal with those impacts," he said on Firstline this morning.
One of those impacts will be more severe weather events, as sea levels rise and increasing temperatures lead to climate instability.
"With so much of our population living on the coast, our cities on the coast and much of our infrastructure vulnerable to sea level rise, that's a biggie for us," says Prof Naish.
"We talk about a metre being potentially the maximum we can expect, but even half-a-metre with the increase in the intensity of storms is going to lead to a major increase in coastal flooding, for example.
"The one-in-100-year storm by the end of the century could become an annual event."
The report shows New Zealand's wet areas will get wetter, while droughts will become commonplace in areas already considered dry, such as Northland and the east coast of both the North and South Islands.
"That obviously has significant implications for how we future-proof our climate-sensitive primary industries, has implications for water resources, for hydro electricity generation, for a range of issues around those primary sectors," says Prof Naish.
Climate change minister Tim Groser says New Zealand is "committed to doing its fair share to reduce global greenhouse gas emissions", but as mitigating the effects of climate change becomes more difficult, the IPCC says we should be looking at how to adapt.
Prof Naish says New Zealand is "behind the eight-ball" in this regard, suffering an "adaptation deficit".
"I really think we have to be demanding a stronger quality of political leadership, of decision-making," he says.
"It's always tough for governments to make decisions around climate change when there's still some uncertainty around the impacts. But I think what this report makes very clear is that the science is very clear, the impacts are very clear and while we don't know all the answers, it's certainly time to take action."
The IPCC report will be released this afternoon at 1pm, NZT.