An honorary academic wants New Zealand to cut emissions, after research found the world's oceans were hotter than ever before in 2021.
Previous ocean temperature records were set in 2020 and 2019.
Dr Kevin Trenberth from the University of Auckland said warmer ocean temperatures are a clear indicator climate change is continuing.
"There's a lot less variability or noise, if you'd like to think of it that way, in the ocean record than there is in the atmospheric record, or the surface temperature record."
An EU climate change service found 2021 was the fifth hottest year on record for the globe, while research from NIWA found for New Zealand specifically it was the hottest year ever.
Trenberth said people may think if the global surface temperature is not rising every year it will be fine, but the problem remains.
"People might look at the global mean surface temperature record and say, 'oh, we don't have to worry, it hasn't gone up anymore', but it will. It gets knocked down by weather and La Nina, [but] global warming is still with us, it's very strong, the concentrations of carbon dioxide in the atmosphere continue to go up - we have a problem."
New Zealand needs to cut emissions in response, he said.
"New Zealand has said that we are going to try to get to so called net zero, cut down our emissions, but so far, we have yet to take the actions necessary to put us in that direction."
The COP26 conference in Glasgow was supposed to address rising carbon dioxide emissions but, in his opinion, did not do so adequately.