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Scientists: Ocean temperature records are shocking

“The year 2023 has given an ominous new meaning to the phrase ‘far beyond expected’.”

This is how the World Meteorological Organization (WMO) begins its summary of the past year State of the Climate Report 2023. The summary is an enumeration of the impacts of climate change, and a number of records have been completely broken.

The report confirms that 2023 was the hottest year on record. The average global temperature was about 1.45 degrees higher than in pre-industrial times. Globally, each month from June to December set record high temperatures for the month in question. The past decade is the warmest ten-year period on record.

– We have never been closer – even temporarily at the moment – to the 1.5 degree minimum in the Paris Agreement, says WMO Secretary-General Celeste Saulo.

Celeste Saulo, Secretary-General of WMO.

Photograph: Marcial Trezzini/AP

root cause It is global warming that has been reinforced since last summer by the El Niño climate phenomenon and its warming effect.

– I'm not surprised, the weather is highly expected to continue to warm. But I'm very worried. Extremes similar to those we see today will occur and will get worse. It's an ongoing process that is in principle inevitable, says Erik Kjellström, professor of climatology at SMHI.

Emissions must be reduced quickly if we are to avoid the worst-case scenarios. There are many scientific articles that show this very clearly.

Of all the records last year Is sea temperature what most worries and confuses scientists? Globally, surface water temperatures have reached record levels since last spring. The World Meteorological Organization points in particular to warmth in the North Atlantic. At the end of 2023, there were widespread extreme heat waves, with temperatures exceeding average by 3 degrees.

Ola Kalin, oceanographer at SMHI

Photo: Johan Rowlandson

The temperature does not match the warming patterns associated with the El Niño phenomenon.

For many who closely follow developments in the oceans, what we see is shocking. Records are broken on the assembly line by very large margins. It turned out to be much worse than expected. There is also no scientific explanation yet for why the situation has deteriorated to this extent, says Ola Kalin, an oceanographer at SMHI.

– Climate warming and the El Niño phenomenon are not sufficient to explain extreme values. The situation was worse in the North Atlantic, which has now held record temperatures for more than 365 days.

Researchers have pointed to, among other things, a volcanic eruption in the sea off Tonga and reduced sulfur emissions from ship fuel as contributing causes. Lower emissions have resulted in fewer particles in the air, which increases solar radiation and therefore heating as well. But the uncertainty is great.

Switzerland's glaciers have lost a tenth of their remaining volume in the past two years

Image: NASA

During 2023 it was affected On average, nearly a third of the world's oceans are affected by marine heatwaves that damage ecosystems and food systems, according to the World Meteorological Organization. By the end of the year, more than 90% of the oceans experienced a heatwave at some time during the year.

– The fact that we are in this situation so far with just over 1 degree of global warming is scary when we know that with today's inadequate climate policy we risk about 3 degrees of global warming by 2100. What will the state of the oceans be like? – says Ola Kalin: “It's terrifying to think that at that time, all the tropical coral reefs will be completely dead.”

Corals are sensitive to heat. When the water becomes too warm, coral expels the colorful algae that live in its tissues and turns white. They can recover but if the temperature is high for too long the coral dies. According to the Intergovernmental Panel on Climate Change, all coral reefs are at risk of dying when global temperatures rise by 2 degrees.

In the northern parts of Australia's Great Barrier Reef, widespread coral bleaching is now occurring. This is the fifth time in eight years that this has happened on a large scale. “What is happening on the reef now can be described as an underwater forest fire,” climate scientist Simon Bradshaw told Reuters news agency.

The Rhone Glacier in Switzerland will be covered in the summer of 2023 in an attempt to prevent it from melting.  Glaciers in Switzerland have lost a tenth of their volume over the past two years

Photograph: Matthias Schrader/AP

Rate of sea level rise It has increased sharply. During the ten-year period 2014-2023, it averaged 4.77 mm per year. This is more than double compared to the ten-year period 1993-2002, when it was 2.13 mm per year. Much of the level rise is because warmer water takes up more space, but melting ice sheets are increasingly contributing to the rise. It is now estimated that about one millimeter per year comes from ice sheets.

There are two main ice sheets on Earth: the Greenland Ice Sheet and the Antarctic Ice Sheet. Average ice mass loss has more than tripled since the 1990s: increasing from 105 gigatons per year in 1992-1996 to 372 gigatons per year in 2016-2020.

Last year, the extent of sea ice in Antarctica was the lowest on record. The maximum spread was 1 million square kilometers less than in the previous record year – the difference is as large as France and Germany combined.

In the Arctic, sea ice extent was the sixth lowest on record.

Switzerland's glaciers have lost a tenth of their remaining volume in the past two years. In western North America, during 2020-2023, glaciers lost nearly a tenth, or 9%, of the volume they had in 2020.

Melting ice and warming seas It is a development that will continue for a long time to come, hundreds and perhaps thousands of years, even if emissions decline sharply and quickly.

Erik Kihlström is a professor of climatology at SMHI.

Photo: SMHI

-Once the oceans warm, the process continues for a long time. It takes much longer to restore large land ice than to collapse. You can see that in Earth's history, in ice craters, the accumulation of ice is much slower than the melting, says Erik Kihlstrom.

Last year, extreme weather and climate events, such as major floods, tropical cyclones, extreme heat, drought and associated wildfires, had major social and economic impacts on all inhabited continents.

Tropical Cyclone Mocha May was one of the strongest cyclones ever seen in the Bay of Bengal. This displaced 1.7 million people from Sri Lanka to Myanmar and via India and Bangladesh, exacerbating acute food insecurity.

Long periods of drought affecting northwest Africa, parts of the Iberian Peninsula, parts of central and southwest Asia, and parts of Central and South America, have led to poor harvests and low levels of water storage.

– The El Niño phenomenon has begun to decline now, and expectations indicate that we are heading towards neutral conditions during the early summer and then the La Niña phenomenon, which has a cooling effect, towards the fall. But perhaps we can rely on higher ocean temperatures for a while longer, says Ola Kalin.

Read more:

The global temperature is 1.56 degrees higher than in pre-industrial times

Scientists: Temperatures could reach new highs this summer

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