A damning international report on mankind's role in climate change should be a wake-up call for urgent action, New Zealand environmentalists say.

The UN Intergovernmental Panel on Climate Change's draft fifth assessment report, released on Friday night, found it was "extremely likely" that humans were responsible for more than half the rise in global temperatures in the last six decades.

The landmark report, the IPCC's strongest warning yet, said if the world could not cap carbon emissions to one trillion tonnes, a budget already half spent, then global warming could not be held to within 2C.

The report said the world's climate would have warmed by at least that much by the end of the century, causing widespread extreme weather, drought and rising sea levels around the world.


The 2000-page report, which had some 250 lead authors and drew on thousands of peer-reviewed articles, updates the IPCC's 2007 report, which stirred controversy after critics found some errors.

The likely impacts of climate change on New Zealand could include rising sea levels, increases in the severity and frequency of coastal storms, and more floods, landslides and droughts.

Conservation group WWF New Zealand said the report was "a wake-up call for all of us" and confirmed the urgent need for action on climate change.

"It is the most detailed analysis of climate science to date and shows that we need to take action now if we are to avoid the worst impacts," WWF campaigns head Peter Hardstaff said.

New Zealand had renewable natural resources and should be investing in them instead of fossil fuels, he said.

Mr Hardstaff said the risk of ignoring the science was huge.

"The longer we delay action the more expensive addressing climate change will become. The good news is that we have most of the solutions within our grasp but what is most needed is the political will to help implement them."

Green Party climate change spokesman Kennedy Graham said the report was the IPCC's strongest warning yet.

"The IPCC has delivered a stark message - the climate is changing and we need to immediately reduce our greenhouse gas emissions dramatically to prevent runaway warming."

Dr Graham said the Government had buried its head in the sand on climate change.

"There is no excuse for inaction. The climate change threat is real and immediate, and we have the tools to reduce our emissions. It's time to stop prevaricating and get on with the job for the sake of our environment and our economy."