A young Hamilton law student's legal bid to seek a judicial review into New Zealand's climate change pledges has been dismissed by a High Court judge.

But Sarah Thomson said she was pleased that today's ruling on of her case against former climate change minister Paula Bennett and her government had acknowledged the need for action on the issue.

Thomson's lawsuit, heard in the High Court in Wellington in June, asked the former minister to justify the way in which our climate targets under the Paris Agreement had been set.

The case was the first of its kind in New Zealand but was among many to have been mounted against governments around the world in recent times.

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Despite being once dismissed by former prime minister John Key as "a joke", it could open the door to future challenges.

Filed when Ambassador to the US Tim Groser was climate change minister, the suit challenged a claimed failure to review climate targets for 2050 after the UN's Inter-governmental Panel on Climate Change (IPCC) released its Fifth Assessment Report (AR5) in 2013.

It also challenged the Government's target of slashing domestic greenhouse gas emissions by 11 per cent below 1990 levels and 30 per cent below 2005 levels by 2030, which Thomson argued was "unreasonable and irrational" against the seriousness of the issue.

Thomson sought an order requiring the minister to set a new 2050 target that - if "adopted by other developed countries in combination with appropriate targets set by developing countries" - would stabilise greenhouse gas concentrations at a level that would prevent dangerous effects.

She alleged that the setting of our climate targets had been unlawful and requested a judicial review.

Bennett had argued she was comfortable the target had been fair and ambitious and had been set only after a thorough process of consultation.

Her lawyers also stated the government did not need to set a target that strengthened the global response to climate change to hold warming to below 2C.

In her decision today, Justice Jillian Mallon acknowledged that, after the release of the AR5, the minister had been required to turn her mind to whether there had been any material change as between the AR4 and the AR5 that was relevant to the 2050 gazetted target - and that this didn't happen.

Yet Justice Mallon noted this challenge had been overtaken by a new government which had already announced it intended to set a new 2050 target.

And she further stated she was not persuaded the minister made "any reviewable error for which the court may intervene", and that the international framework had been followed.

"The international process envisages review and demonstrated progression by developed countries including New Zealand," Mallon stated.

"Quite apart from the international process, New Zealand remains free to review its 2030 target (or any other target) as it considers appropriate.

"The community has elected a new Government and it is for that new Government to weigh the competing factors and to reach a view about the appropriate targets going forward."

She dismissed Thomson's request for a judicial review, with a preliminary view that court costs should lie where they fell.

Despite the ruling, Thomson told the Herald she felt the case had been "a big win" in some areas - namely that it showed the courts were able to hold ministers to account when making important decisions on climate change.

"We were challenged by the government that we couldn't even seek review and obviously there was no issue in that, so in that sense, there was almost a win there.

"And also, the judge acknowledged that a lot of things we brought up were for mandatory consideration, so that gives some guidelines for future ministers as well.

Thomson further felt the case, which attracted a gathering of supporters to the courthouse, among them prominent climate scientist Professor James Renwick, had done much to highlight climate change.

"You can never measure these things in a concrete way, but I really hoped it had been at least successful in bringing peoples' attention to the issue and making them aware that we are not doing enough about it.

The ball was now in new Climate Change Minister James Shaw's court, she said.

"Time is of the essence - and we will be watching closely."

New Zealand and climate change

• Under present projections, the sea level around New Zealand is expected to rise between 30cm and 100cm this century. Temperatures could also increase by several degrees by 2100.
• Climate change would bring more floods; worsen freshwater problems and put more pressure on rivers and lakes; acidify our oceans; put even more species at risk and bring problems from the rest of the world.
• Climate change is also expected to result in more large storms compounding the effects of sea-level rise.
• New Zealand, which reported a 23 per cent increase in greenhouse gas emissions between 1990 and 2014, has pledged to slash its greenhouse gas emissions by 30 per cent from 2005 levels and 11 per cent from 1990 levels by 2030.
• The new coalition Government has promised greater action, with a proposed new independent Climate Commission and Zero Carbon Act and goals for a carbon-neutral economy by 2050 and 100 per cent renewable energy by 2035.