For a while scientists have been warning that as the oceans warm up their ability to absorb carbon diminishes. Now new research from the Sea of Japan will heighten fears that the Earth is rapidly slowing down in its natural ability to absorb man-made CO2.

Scientists found that there had been a sudden and dramatic collapse in the amount of CO2 being absorbed by the Sea of Japan. This is deeply worrying: The world’s oceans soak up about 11 billion tonnes of human C02 pollution each year, about a quarter of all produced.

It goes without saying that even a slight weakening of this natural process would leave significantly more CO2 in the atmosphere. Kitack Lee, an associate professor at Pohang University of Science and Technology, who led the scientific research, says the discovery is the “very first observation that directly relates ocean CO2 uptake change to ocean warming”.

According to Lee, warmer waters alter a process known as “ventilation” – the way in which seawater flows, then drags absorbed CO2 from surface waters to the depths. He warns that the effect is probably not confined to the Sea of Japan. It could also affect CO2 uptake in the Atlantic and Southern oceans.

Announcing their results in the journal Geophysical Research Letters, the scientific team led by Lee argue: “The rapid and substantial reduction … is surprising and is attributed to considerable weakening of overturning circulation.”

This is likely to be the first of many new scientific studies this year that show that climate change is having even greater impacts than previously thought.