World's sea surface temperatures hit record high in 2023

The world's oceans have just seen their hottest year on record. 

The first report collecting 2023's entire temperature data set has just been released, and it has found global sea surface temperatures smashed previous records in every month after May.

It's called the blue planet for a reason.

"This is the first published record on what has just happened in 2023, dealing with the ocean heat content," said Kevin Trenberth, the report's co-author.

It's the work of 34 specialists from around the globe. Trenberth is one of them and he told Newshub the findings are clear. 

"2023, for the ocean, is the warmest year on record."

The data is collected by Argo floats, which are robotic cylinders that give near real-time readings on temperature and salinity.

The Argo floats project is an international collaboration of 30 countries - and there are almost 4000 of them in the ocean.

In 2023, the average sea surface temperature was a record 0.6C higher than the long-term trend between 1981 and 2010.

"The increment over all the previous years - was so much larger than we've ever seen before and this has astounded scientists," said Trenberth.

A graph showing trend lines in global sea surface temperature changes. The white line on top is 2023.
A graph showing trend lines in global sea surface temperature changes. The white line on top is 2023, which was an "astounding" 0.6C higher than the long-term average. Photo credit: Newshub Graphics.

It's also causing havoc on marine ecosystems, harming species right at the bottom of the food chain.

"Phytoplankton, all the way up to fish."

Sponges are also a vital source of food for coastal fish, but the hot temperatures have been a killer.

"They just get impacted over such large areas, it's mind-boggling," said Arie Spyksma, research fellow at Waipapa Taumata Rau / University of Auckland.

"Tissue is dying because they can't cope with the heat, and that potentially impacted hundreds of thousands of sponges over hundreds of kilometres of coastal reef," he told Newshub.

And while the natural cycle of El Niño has partly helped to bump up the temperature, Trenberth said there's one thing to blame more for the records than anything else.

"The burning of fossil fuels primarily," he said.

"The increment over the last year was as large as it's ever been. About 3ppm (parts per million) by volume."

"You know we can't keep waiting for the climate to get worse, it is worse, and if we want to fix it and potentially prevent some of the impacts we're starting to see from getting worse. We need to act now," said Spyksma.

An ominous warning that temperatures will keep rising if carbon dioxide (CO2) emissions aren't cut radically and quickly.