Rising ocean temperatures will make severe weather events such as cyclones more catastrophic, according to GNS climate scientist Georgia Grant.
She told Morning Report that while the Paris target was keeping the global average temperature rise to two degrees Celsius, New Zealand oceans would actually rise by four degrees.
"The regions do and will express that warming differently," she said.
"Simply put, warmer seas equals more energy in the system, so more of those extreme weather events that we've been seeing."
That includes the rain dump in Auckland and "the devastating Cyclone Gabrielle".
Sea ice around Antarctica had not been growing this winter and that would have significant flow-on effects for New Zealand as well, Grant said.
The warmer seas were not a surprise to her.
"Our oceans and atmosphere are what transfer that heat around the Earth and obviously as we warm and we're warming the tropics that heat's gotta go somewhere and so it's coming down past New Zealand."
She said this was simply another reminder about the urgency to act now on climate.