Climate scientists alarmed at speed of ocean warming

The sea is warming at a faster rate than thought, according to the largest analysis of its temperatures so far.

‘Studying ocean temperatures is a better way of understanding climate change in the future.’ A mother and child walk along a beach at sunset in Cyprus last month. Picture: Petros Karadjias/AP

The sea is warming at a faster rate than thought, according to the largest analysis of its temperatures so far.

The vast majority of the extra heat from climate change is stored in the oceans but until recently there were few reliable methods of measuring it.

Researchers have now combined findings from multiple studies to show there has been a consistent warming trend even during the so-called hiatus, a 15-year period at the beginning of this century when land temperatures seemed to hold.

The latest study combined previous estimates to show that ocean warming is accelerating at a rate 40 per higher than was thought.

Researchers said this showed that, contrary to the claims of some sceptics, the world was warming at a rate that corresponded to that predicted in climate models.

Zeke Hausfather of the University of California, Berkeley, said that it was almost impossible to understand climate change unless you could measured sea temperatures. “If you want to see where global warming is happening, look in our oceans,” he said.

“Ocean heating is a very important indicator of climate change and we have robust evidence that it is warming more rapidly than we thought.”

It is estimated that about 93 per cent of all heating occurs in the oceans, unnoticed by traditional meteorological stations.

His paper, published in the journal Science, in part took advantage of a fleet of 4000 submersible buoys called Argo.

For over a decade they have drifted through the world’s oceans, diving as much as two kilometres before surfacing to provide readings of salinity, temperature and pH (acidity).

Using the data from these, combined with improved analysis of older measurements, three teams separately estimated the heat content of the oceans going back over 40 years.

Another group used a completely different method. As the oceans warm, they emit gases. By looking at the oxygen and carbon dioxide expelled from oceans since 1991, the researchers were able to independently produce their own estimates for warming.

Mr Hausfather said studying ocean temperatures was also a better way of understanding climate change in the future.

While surface temperatures are highly variable, seas are far less volatile. This means that the trend unaffected by the fluctuations caused by other factors such as volcanoes or El Nino.

“You can see a far clearer signal,” Mr Hausfather said.

“Ocean heat content tends to increase year on year. In the oceans 2018 is going to be the warmest year, just like 2017 was the warmest before that, and 2016 before that.”

Tom Whipple is Times science editor.

The Times