Disappearing clouds are to blame for the “crazy” rise in ocean temperatures, scientists have warned.

A policy introduced in 2020 to cut the amount of sulphur emitted by ships resulted in an 80 per cent reduction of the element in the Earth’s atmosphere.

The International Maritime Organisation (IMO) demanded that the sulphur content in fuel be cut from 3.5 per cent to 0.5 per cent for all vessels operating worldwide.

The policy resulted in fewer build-ups of the element in clouds and less cloud coverage overall.

But this has increased the warming effect of carbon emissions by 50 per cent, partly because the sun heats the seas more effectively when the skies are clearer.

On Tuesday, the average sea surface temperature reached 20.96 degrees Celsius, the hottest it has ever been.

“This year it’s been crazy,” Tianle Yuan, an atmospheric physicist at Nasa, told the American Association for the Advancement of Science.

Warmer waters cannot absorb carbon dioxide as efficiently, meaning more of it remains in the atmosphere.

This can have dire consequences for marine life and can cause predatory animals such as sharks to become more aggressive.

Yuan’s research, which was published last year in Science Advances, found sulphur clouds, or “tracks” decreased by more than 50 per cent in the main shipping corridors after the IMO regulation was introduced.

Michael Diamond, an atmospheric scientist at Florida State University, published similar findings in the Atmospheric Chemistry and Physics journal last week.

Emissions of greenhouse gases trap heat that the oceans absorb steadily and are a primary driver of climate change.

Another influence has been recent weather patterns which have suppressed cloud formation, allowing the ocean to bake in the sun.

But the huge reduction in the number of ship fumes has also contributed to climate change, according to the studies.

That trend is magnified in the Atlantic Ocean, where maritime traffic is particularly heavy. This is because cloud coverage does not reflect as much light and heat from the sun, resulting in a warming effect of the earth.

The experiment unintentionally engineered by the IMO rules is providing a rare opportunity for scientists to study a geoengineering scheme in action, although it is working in the wrong direction.

One strategy called “marine cloud brightening”, which would see ships inject particles back into the air to make clouds more reflective, could be used to slow global warming.

Diamond even suggested additional particles could be introduced to the clouds to boost cloud density and in turn its reflective properties which would help reverse the current trend.

The Daily Telegraph, London