"I don't think there is any other region but the Pacific with the moral authority to tell the world that the world needs to abide by what the scientific community is telling us," he said.
He praised the Government's zero carbon legislation, saying the move was "absolutely crucial".
Last Wednesday, the Government introduced the much anticipated, and much delayed, zero carbon legislation to Parliament.
Ardern and Climate Change Minister James Shaw both described it as "ambitious" but necessary.
It commits to what is called a "split target" – aiming to reduce all greenhouse gas emissions, aside from biogenic methane, to net zero by 2050.
Biogenic methane – the emissions created from livestock such as sheep and cattle – is not completely exempt as the bill commits to reducing it to 10 per cent below the 2017 levels by 2030.
The bill also commits to reducing gross emissions of biogenic methane to between 24-47 per cent below the 2017 levels, by 2050.
As well as his trip being one of gratitude for the Government's work to fight climate change, he also said it was one of solidarity.
"Solidarity with the victims of Christchurch, with their families, with their communities, but also with the people and the Government of New Zealand," he said.
On March 15, a gunman opened fire in two mosques in Christchurch, taking the lives of 51 people.
Guterres said that every year, since he was the UN's High Commissioner for refugees, he has paid a solidarity visit during Ramadan to a different country.
As Secretary-General he has been to Afghanistan and Mali, but this year he decided he would do his solidarity visit in Ramadan to Christchurch.
He wanted to pay tribute to their courage, resilience and the extraordinary unity of the people of Christchurch.
He said he admired Ardern's leadership in the aftermath of the terror attack.
Ardern told media today she had first met Guterres several months ago where the pair spent "quite a bit of time" talking about climate change and the impacts it would have on the Pacific.
"At that time, I suggested a visit to the Pacific would really be warmly welcomed," she said, adding it would be an opportunity to highlight the impact climate change will have in the region.
"The fact that you have followed up, and you are here, is of great delight to us."
She thanked Guterres for the leadership he has shown on climate change too.
