"The AR5 is hugely significant for New Zealanders, and for all nations - it is the one best resource for our present understanding of climate change."
Dr Renwick's chapter of the report examines how patterns of climate variability, such as El Nino and monsoons, are changing and how this could affect different global regions.
The chapter leads in to a section looking at how climate change would touch people and infrastructure.
Though New Zealand's location would likely mean our average climate rise would be one degree less than the 4C predicted to transform Northern Hemisphere countries such as the United States, Kiwis would still see big differences, Dr Renwick said.
"What we'd call a cold year in 2090 is what would be called an exceptionally warm year now."
He described climate change as the biggest issue facing humanity, with political and social responses urgently required.
But the AR5 stopped short of telling world leaders what to do.
Rather, it would demonstrate a vast breadth of changes already happening, with the long time-lags built into the climate system.
"The last time greenhouse gas levels were as high as they are now, global sea levels were about 20m higher than they are now - big oceans and ice sheets take centuries to adjust, but adjust they do."
Unless the world could reduce its greenhouse gas emissions to near-zero by mid-century, he said, our children and their children would be consigned to dealing with global disruptions unprecedented in the history of civilisation.
"Even if we do cut greenhouse gas emissions to zero soon, the oceans will continue to rise for many centuries anyway, and the global climate will change by at least as much as it has in the past 100 years."
Nevertheless, the AR5 was still expected to affect domestic policy, simply by putting climate change response "front and centre" with governments everywhere, he said.
Yet even though the fundamental messages were spelled out in detail by 2007's AR4, Dr Renwick felt there remained a lack of political will - or even a sense of reality - to restrain climate change.
"There is much talk at the international diplomatic meetings about limiting global warming to two degrees, but there is absolutely no effective action.
"The opportunity to meet that two- degree target has passed, unless something truly miraculous happens in the next five years."
Governments could lead in slashing greenhouse gas emissions by investing in research on renewable technologies, public transport and phasing out fossil fuel exploitation.
New Zealand had held a high profile around many issues including human rights, social welfare and nuclear weapons and it could do so with climate change, he said.
"Such moves have the potential to be of huge benefit to the New Zealand economy."
Professor David Frame
Developing nations critical
A leading climate scientist has taken aim at shortcomings of the Kyoto Protocol in his inaugural professorial lecture.
Professor David Frame, director of the New Zealand Climate Change Research Institute at Victoria University, said the protocol only regulated a small and shrinking fraction of emissions - yet placed no obligations on the developing world.
Commenting on themes of his lecture in Wellington this month, Professor Frame told the Herald serious inroads could not be made into tackling climate change without the participation of developing nations.
Without climate policy, around 70 per cent of warming would come from the developing world by 2100.
"Rapid growth in emissions in the large emerging markets is bringing significant improvements in standards of living to people in cities in Brazil, China, and so on, but it actually forms a serious threat to those very poor people most at risk from climate change."
He also criticised the Kyoto Protocol for lacking "any meaningful compliance mechanisms".
"Basically, nothing much happens if someone agrees to a target and then fails to meet it, so the treaty struggles to push people to take on burdens beyond those they'd take on with no treaty at all."
In November, Climate Change Minister Tim Groser announced New Zealand would not be signing up to fresh commitments under the protocol, joining Japan, Canada and Russia in pulling out.
Instead, New Zealand has joined a non-binding framework which includes the United States and major developing countries such as China, Brazil and India.
At the time, Mr Groser said he did not see the point in committing to a treaty which represented less than 15 per cent of global emissions.
Professor Frame was relaxed about New Zealand dropping out - a move that drew fire from environmental quarters - but said there was scope for New Zealand to play a role in ensuring future international arrangements were well-designed.
"And, like everyone, we have reputational capital on the line - we have a history of liking to see ourselves as a good global citizen," he said.
"Economically, substandard efforts on climate change could come back to harm us given our reliance on agriculture, a sector where big players love looking for opportunities to enact protectionist policies.
"But in terms of our direct impact through our emissions we're pretty small change - for us it's really about being a constructive part of a global solution."
Professor Frame saw the international post-2020 climate change regime as being "absolutely fundamental" to tackling the problem.
"Climate policy has to mature, and fast. Climate change is a long-term issue, so we should plan for a sustained, global response over several decades."
While one strand of thought argued that the climate change problem needs to be chopped up into pieces that were easier to solve, another argued that deep cuts in emissions would require a tightly integrated framework, he said.
"I think it's a question of feeling our way a bit - trying various approaches and seeing which seem the most promising.
"Given that climate policies are only effective if they can command electoral support, I think it's important that climate initiatives become a mainstream part of other policies, rather than as radical social experiments."
Dr Simon Lamb
Doco tracks climate science from Arctic to Antarctica
Spurred on by constant attacks from sceptics, Victoria University's Dr Simon Lamb set out to gain an understanding of climate science from those who know it best - the scientists.
Six years later, his global odyssey has culminated in a user-friendly documentary that seeks to give a voice to the climate science community.
"As a scientist - a geologist, in fact - I felt that the unprecedented attacks on climate scientists, with accusations of fraud and a hoax, were bringing all of science into disrepute, so I wanted to see for myself what climate scientists were like, what sort of research they did, and what they think," he said. "However, I was not expecting this to turn into a personal journey lasting nearly six years."
His 73-minute film Thin Ice follows the work of researchers on four continents as they study the changes in the atmosphere, oceans and ice sheets through measurements and computer modelling.
A collaboration between Victoria University, Oxford University and London-based DOX Productions, the film is part of a wider project to communicate the science of climate change to a wide audience.
The Thin Ice website, launched this month, has been developed over the past year to include 40 short videos as well as some background on the 30 scientists involved.
The film itself will be made freely available from the website for a global screening on Earth Day, on April 22, and after that for a fee.
"'The film chronicles my personal journey to find out directly from climate scientists why they think that our emissions of carbon dioxide and other greenhouse gases are changing the planet's climate," Dr Lamb said.
"In fact, the film is almost entirely in the words of the scientists, and I am really only the glue that holds what they say together.
"However, by watching the film, you not only find out what the scientists think, you also see for yourself the research being carried out, whether it be on the polar plateau in Antarctica, at -40C, or in a storm on the southern ocean, or back in the laboratory." Dr Lamb said it was his visit to the Arctic that really opened his eyes to the reality of global warming.
"Temperature records show that this is one of the fastest warming places on the planet, but these results have been contested by some climate sceptics.
"Yet, you only have to talk to the local inhabits - for example, the Sami people of northern Norway - to realise that they know it is warming rapidly from their own observations."
At the other end of the Earth, his research in Antarctica brought home to him the vulnerability of the great ice sheets to future global warming.
"I filmed the deep drilling into the rocks beneath McMurdo Sound, which shows that a few million years ago, when the level of carbon dioxide in the atmosphere was only marginally higher than today, the ice in west Antarctica must have completely disappeared, with at least five metres of sea level rise and huge impacts on the ocean circulation and life in the Southern Ocean," he said.
"This is a clear indication of the sort of future we are currently heading for with our global emissions.
"This is an example of science at its best, not worst. In fact, it has given us a great gift, the ability to look into our future and shape it.
"The film does not set out to tell the audience what we should do about climate change, but rather, what we know about it."
Read more: More droughts and bush fires tipped for future
On the web
www.thiniceclimate.org
