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Ocean heat record broken and experts fear temperatures could rise even further

 The Mediterranean Sea reached its highest temperature on record on July 25, Spanish researchers said.
The Mediterranean Sea reached its highest temperature on record on July 25, Spanish researchers said. Copyright JOSE JORDAN / AFP
By Rosie Frost
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Ocean temperature records are being broken around the world with dire consequences for the health of the planet.


The average surface temperature of the world’s oceans has hit its highest-ever level reaching 20.96C this week, according to the Copernicus Climate Change Service (C3S).

It broke the record of 20.95C set in 2016 and scientists say it is likely that the record will continue to be broken as temperatures are usually highest in March, not August.

It follows a pattern of marine heatwaves and record sea surface temperatures around the world.

The Mediterranean Sea recorded its highest-ever surface temperature last week at 28.71C. Waters around the Florida Keys were similar to the temperature of a hot tub, hitting highs of just over 38C and possibly breaking a world record.

The National Oceanic and Atmospheric Administration (NOAA) also reported last Friday that the North Atlantic may be the hottest it has ever been. And it's getting hotter much earlier in the year with previous records set in September.

The IPCC says that marine heatwaves doubled in frequency between 1982 and 2016. Since the 1980s, they’ve also become longer and more intense.

Experts warn this could have devastating consequences for the health of the planet.

How hot are our oceans?

The North Atlantic usually begins to warm up in March after winter and reaches its peak in September. But records have continuously been broken since April this year.

And the NOAA says that the North Atlantic is only going to get hotter “through the month of August”. It's highly likely that the record will be broken again.

Global average sea surface temperature has been “well above” the values previously seen at this time of year, according to C3S. The climate change service says that the high sea surface temperatures contributed to the exceptionally warm July seen around the world.

AP Photo/Rebecca Blackwell, File
People swim in the ocean off of Crandon Park, July 28, 2023, in Key Biscayne, Florida.AP Photo/Rebecca Blackwell, File

The high temperatures are likely being driven in part by the El Niño weather phenomenon. This occurs when warm water rises to the surface in the South Pacific and pushes up global temperatures.

So far the current El Niño is still weak which means ocean temperatures are likely to rise even further as it develops.

But these weather patterns are also being exacerbated by climate change.

“The more we burn fossil fuels, the more excess heat will be taken out by the oceans, which means the longer it will take to stabilise them and get them back to where they were,” Dr Samantha Burgess from C3S told the BBC.

What effect will the world’s warming oceans have?

Oceans play an important role in the regulation of the Earth’s climate. They absorb heat, drive weather patterns and act as a carbon sink.

But as they get warmer they are less effective at doing this job. The cycle means that as ocean temperatures rise, they become less effective at absorbing CO2 leading to an increase in the amount of this greenhouse gas in the atmosphere.

Ice also melts as waters warm increasing the severity of sea level rise. And high ocean temperatures can also increase the chance of hurricanes, cyclones, storms and extreme weather.

Hotter oceans also have an effect on marine life with whales and some fish species moving to cooler waters which upsets the food chain. The record-high temperatures also put corals at risk with reefs off the coast of Florida now facing a severe threat of bleaching due to the marine heatwave.

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