The Prime Minister is not sure whether a New Zealand-initiated debate on small island states at the United Nations Security Council this week will lead to any definitive statement on climate change.
But the Green Party said the council needed to acknowledge climate change was a threat to security to boost the chances of success at UN talks in Paris in December.
During its campaign to get on the Security Council, New Zealand promised small island developing states it would ensure their voices were heard.
They get the opportunity on Friday when the council, under New Zealand's presidency, has an open debate about their circumstances.
Green Party foreign affairs spokesperson Kennedy Graham said climate change had to be at the top of the agenda.
"We've had enough examples, including in our own country - low-lying deltas, small island states, sea-level rise, extreme droughts and floods and intense storms.
"We are in the middle of climate change - it is becoming dangerous," he said.
"Now is the time to get it over the line and have the Security Council declare it to be a threat to peace and security."
On previous occasions when the Security Council has discussed climate change it has refused to call it a threat to security.
Former Prime Minister and international law expert Sir Geoffrey Palmer said it was clear it was a threat.
"It's very difficult to see how some of these small Pacific Island developing states can actually survive as nations, they may be lost," he said.
The ultimate security problem is the loss of a soverign nation and we're staring this in the face here."
John Key said climate change must be taken seriously but he was not sure it was a threat to security.
"It could be - it depends on how you define security of course. Their physical security is one particular issue at point," he said this week.
But Mr Key added he had received advice that climate change was occuring at a slightly faster rate than models predict.
He was unsure whether the Security Council will support a resolution on climate change, while Sir Geoffrey Palmer was also pessimistic.
"I am worried that the Security Council will not do enough," he said.
"The whole record of climate change discussions since 1992, when the United Nations Framework Convention was agreed at Rio, has been to do nothing effective."
But Sir Geoffrey said a Security Council resolution was needed to give the climate change talks in Paris some steel.
Without a Security Council resolution, he said, nations would be under no obligation to take action.