Increasingly powerful cyclones driven by climate change may require a new classification for the storms, category 6.

Cyclone Winston which hit Fiji in 2016 had winds exceeding 230km/h which was the highest margin of a category 5 cyclone, Climate Change Minister James Shaw told Radio NZ.

The Pacific Climate Change Conference is underway in Wellington, attended by politicians, scientists and policy makers.

Scientists were now able to say with some confidence extreme weather events were affected by climate change in some way, Shaw said.

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Climate change was no longer a theoritcal problem, it was something that affected people in every day life, American climatologist Michael Mann said.

"We are talking about a substantial increase in the risk of catastrophic coastal flooding, nowhere is that more apparent than here in the pacific."

However National Institute of Water and Atmospheric Research principal scientist Chris Brandolino said introducing a new category could be complex, as forecasters were trained for 1 to 5 categorys and public knowledge was used to the current categories.

It was an appropriate time for a conference following the passsing of Cyclone Gita two days ago and ex-cyclone Fehi two weeks ago.