Jacinda Ardern says her father knows about the effects of climate change - he's seen them in Kiribati.
In her campaign launch speech in Auckland on Sunday, Ms Ardern called climate change "my generation's nuclear free moment".
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She recalls the moment her father Ross, New Zealand's high commissioner to Niue, piped up in a family conversation about climate change.
"I remember listening to a couple of members of my family discussing climate change a few years ago. It's fair to say they were sceptical," she said.
"I was waiting for my moment to jump in, when suddenly I heard my father pipe up.
"'I don't know much about the science,' he said, 'but I do know what they showed me in Kiribati'."
She says he visited local village leaders who had shown him where the water sat when they were children and where it was now - lapping squarely around their survival.
"There will always be those who say it's too difficult. There will be those who say we are too small, and that pollution and climate change are the price of progress," Ms Ardern said.
"They are wrong."
She says New Zealand has an opportunity to shape its identity by making the transition to reduced emissions.
"This is my generation's nuclear-free moment, and I am determined that we will tackle it head on."