- Written by Matt McGrath, Mark Pointing and Justin Rowlatt
- BBC News Climate and Science
The world’s oceans have been breaking temperature records every day over the past year due to climate change, according to a BBC analysis.
It beat the previous high for this period by nearly 50 days, setting a new record in the satellite era.
Although global warming gases are the main cause, the natural weather phenomenon El Niño also contributes to ocean warming.
Super-hot oceans are taking a toll on marine life, causing a new wave of coral bleaching.
The analysis is based on data from the EU’s Copernicus Climate Service.
Copernicus also confirmed that last month was the warmest April on record in terms of temperatures, extending the monthly record to 11 consecutive days.
For decades, the world’s oceans have been the planet’s “get-out-of-jail-free card” when it comes to climate change.
Not only do they absorb about a quarter of the carbon dioxide that humans produce, they also absorb about 90% of the excess heat.
But over the past year, the oceans have shown the most worrying evidence that they are feeling the heat, especially at the surface, and are struggling to cope.
Starting in March 2023, the average surface temperature of the world’s oceans began to further exceed long-term norms, reaching a record high in August.
According to data from Copernicus, the past few months have been relentless, with sea surface temperatures hitting the world’s highest daily average of 21.09 degrees Celsius in February and March of this year.
As the graph below shows, every day since May 4, 2023 not only broke the daily record for this period, but some days the difference was even bigger.
It took about 47 days to break that year’s daily record by at least 0.3 degrees Celsius, according to a BBC analysis of Copernicus data.
Never before in the satellite era have the differences in records been so large.
The maximum record update dates were August 23, 2023, January 3, 2024, and January 5, 2024, which were approximately 0.34 degrees below the previous high.
Professor Mike Meredith, from the British Antarctic Survey, said: “The fact that all this heat is flowing into the ocean, and that it is actually warming even faster than we thought in some ways, is a huge “It’s a cause for concern.”
“These are real signs that the environment is moving into an area that we really don’t want, and if we continue in this direction, there will be serious consequences.”
Significant impact on marine life
Recent research shows that this human-induced ocean warming is having a profound impact on the planet’s marine life, and may even be changing the seasonal cycle of ocean temperatures.
Perhaps the most significant consequence of the recent warmth is the mass bleaching of corals around the world.
These important marine nurseries turn white and die because the seawater they live in gets too hot. They are an important component of the marine ecosystem and are home to about a quarter of all marine species.
image source, Getty Images
The unusually warm ocean may also have taken a direct toll on emperor penguins, one of the coldest continent’s most beloved marine creatures.
“There have been instances where the sea ice has broken up before the emperor chicks have properly fledged, and there have been mass drownings,” Professor Meredith said.
“Emperor penguins are at risk of extinction due to climate change, which has a lot to do with sea ice and ocean temperatures.”
Rising sea temperatures have caused many species, including barnacles, to disappear from coastlines in the UK.
“The problem with climate change is that it’s happening so fast that evolution can’t keep up,” says Dr Nova Mieszkowska, a marine biologist at the University of Liverpool.
On the coast of Wales, a team from Aberystwyth University is tracking changes in Cardigan Bay’s marine population using the same technology used by police at crime scenes.
DNA signatures collected from water samples revealed that several invasive species were thriving, including the sea squirt, which is thought to be native to Japan and grows like a carpet on the ocean floor.
Professor Ian Barber, director of life sciences at Aberystwyth University, said: “They prevent native species from growing in the areas they colonize.” “Because they operate so well in our environment, they have the potential to occupy large areas of the ocean floor.”
More invasive species appear to be responding more strongly to global warming and rising water temperatures, Professor Barber said.
El Nino phenomenon
In addition to human emissions of greenhouse gases, one of the key factors that significantly affected the world’s oceans last year was the El Niño phenomenon.
The El Niño phenomenon causes warm water to appear on the surface of the Pacific Ocean. As a result, it tends to push up the global average.
But other ocean basins not normally affected by El Niño are also experiencing record ocean heatwaves, and scientists are trying to figure out exactly what’s going on.
“The Atlantic Ocean is warmer than usual, which is not the pattern you would normally associate with El Niño, so somehow something is different,” explains Copernicus director Carlo Buontempo.
This heat continues in many ocean basins, including the tropical Atlantic.
“There are still large areas of warmer-than-normal water in the tropical Atlantic Ocean. [and] This is the main area of tropical cyclone development,” explains Dr. Buontempo.
“Atlantic sea surface temperatures are almost a month ahead of their annual cycle. […] So this is an area that requires attention. ”
Researchers warn that beyond these short-term effects, there will also be long-term consequences that society will have to adapt to.
image source, Getty Images
For example, melting ice sheets and deep ocean warming may continue to drive sea level rise for centuries to come.
“When we talk about climate change, we tend to reduce it to surface changes because we live there,” said Angelique Mele, a researcher at Mercator Ocean International.
“But the deep sea is also one aspect of it.” [of global warming] It promises us centuries and millennia. [climate] change. “
But Mele emphasizes that this is no reason to give up on reducing emissions.
“Depending on our actions, we can slow the rate of warming and reduce the overall amplitude of warming and sea level rise.”
Graphics by Erwan Rivault, Muskeen Liddar, Mark Poynting