Climate Change Minister James Shaw discusses the Zero Carbon Bill at Hamilton's Claudelands Events Centre on Thursday night.

It's yet to be put into writing but already the Government's Zero Carbon Bill is provoking willing debate.

Climate Change Minister James Shaw, flanked by Environment Ministry staff, was in Hamilton on Thursday evening to explain the bill and its broad intentions.

The bill aims to reduce NZ's greenhouse gas emissions and will set in law a "net zero" target for 2050.

In effect, it means the country will have to reduce its emissions as much as possible. Any remaining emissions will be offset through planting more trees.

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Under the bill, a climate change commission will also be set up, although the extent of its powers has yet to be determined.

Fourteen public meetings on the bill have been scheduled across the country during June and July, Shaw said, with feedback informing the drafting of the bill.

However, choosing not to reduce greenhouse gas emissions wasn't an option, Shaw said - an assertion that drew challenges from some in the audience.

"New Zealand has always had dramatic weather, anyone who's been around for a while knows that," he said.

"But the frequency and the severity of storms, and coastal and river floods, droughts, and wild fires, is increasing and will continue to increase as long as we, and the rest of the world, continue to put greenhouse gas emissions into our atmosphere."

In reply, drystock farmer Gavin Shewan said large economies, such as China, were only paying lip service to efforts to reduce greenhouse gas emissions.

Moreover, scientific data appeared to show average global temperatures had dropped over the past two years, he said.

"Europe and Russia had probably the coldest winter in 100 years and it's quite possible that we're going to have a pretty cold winter this year. I ask you why should we do something?"

Similarly, Alastair Brickell, who described himself as a geologist, said there was no evidence carbon dioxide emissions contributed to global warming.

"Why isn't it an option to do nothing?" Brickell asked Shaw.

"Carbon dioxide is our friend. Carbon dioxide is food for plants. We need more carbon dioxide, not less."

Shaw said there wasn't a scientific research institute in the world that would support Brickell's views.

Instead, the Government had to be guided by established science.

"It's very clearly told us for a number of years that there is human induced global warming, based on essentially industrial-era emissions of primarily carbon dioxide but also other greenhouse gases as well," Shaw said.

"So therefore the option of doing nothing would lead to ... increased flooding and fires and droughts and storms as has been increasing over the past couple of decades in New Zealand."

Waikato Regional Councillor Tipa Mahuta said the region was already dealing with the effects of climate change and severe weather events.

At Port Waikato's Sunset Beach, half the car park had been washed away by the sea.

"We're in this conversation about whether to save that car park or whether to give it up," Mahuta said.

Shaw also visited the Fieldays on Thursday to discuss the Zero Carbon Bill with farmers.

He said the bill had been met with "guarded curiosity" from the rural community, but most discussions had been constructive.

There had been an enormous shift in attitudes and environmental practices among farmers over the past decade, Shaw said.

"If you think back 10 years ago, or whenever it was, to tractors being driven up the steps of Parliament, those days are well behind us."

Many farmers still had an "entirely reasonable" sense of concern about how the country would transition to a low-emissions economy.

The bill is expected to be introduced into Parliament later this year, with a view to passing the Zero Carbon Act by mid-2019.