Great Barrier Reef already been dealt its death blow - scientist

An Australian climate scientist has told a conference it's likely Australia's Great Barrier Reef has already been dealt its death blow.

Leading climate scientist Joëlle Gergis of the University of Melbourne told the Climate Change and Business Conference in Auckland that 80 per cent of the reef was bleached in April, the first time damage had extended so far along the reef.

"Scientists know... it's likely that the extensive reef wide bleaching of this year has dealt the largest living structure on this planet its death blow," she said.

"It's just not possible for some ecosystems to adapt to climate change and its dangerous to pretend that they can."

The world's top climate science body has projected only one per cent of the world's coral reefs would be left after 2 degrees Celsius of global heating. Over 1C has already occurred.

Gergis said solutions for up to 80 per cent of planet's greenhouse emissions already existed, but there was not enough political will to act.

"We are failing to address the problem... in fact we are continuing to do harm."

She said New Zealand would experience less pronounced warming than Australia but a central estimate would still see New Zealand experience double the warming it had already experienced so far, by 2100.

A best case scenario, where all countries met their full promises under the Paris Agreement, would still give the planet only only a 14 percent chance of keeping global warming to 1.5C, she said.

She said capturing carbon and storing it underground was not proven to be reliable and it was risky to rely on it.

"While methane or natural gas is still being talked about as a transition fuel... burning of gas will exacerbate global warming in the near term."

"Although some people might try to argue black is white and white is black... The more sensible thing to do here is stop generating new emissions," she said.

Later in the conference, Westpac's head of Sustainable Finance Joanna Silver said New Zealand risked being left behind now that the Australian Government had moved from disbelief in climate action to "throwing the whole weight of its economy" behind it.

She said Australia's about-turn could create opportunities for New Zealand businesses, and they may find Australia more attractive to base themselves in unless there were opportunities here.

She said New Zealand was used to moving in lockstep with Australia but was now falling behind both it and other trading partners, and losing market access as a result.

"These markets are moving faster than we are," she said.