Oceans hit unprecedented heat highs five years in a row: study

The ocean temperatures in 2023 have once again shattered records, and the warming trend will persist throughout this century, even if greenhouse gas emissions were to be halted, according to a new study.

The annual research, published on Thursday in the journal Advances in Atmospheric Sciences, was conducted by a multinational team of scientists from 17 research institutes, spanning China, the United States, New Zealand, Italy and France. They found that last year was the hottest on record for the world's oceans for the fifth consecutive year.

Cheng Lijing, a researcher at the Institute of Atmospheric Physics under the Chinese Academy of Sciences and lead author of the study, said ocean warming is a key indicator for quantifying climate change, as more than 90 percent of global heat ends up in the oceans.

"Oceans also control how fast the Earth's climate changes. To know what has happened or what will happen to the planet, answers can be found in the oceans," Cheng said.

Compared with 2022, the previous hottest year ever recorded, the upper 2,000 meters of the Earth's oceans have absorbed a larger amount of heat, which is "equal to boiling away 2.3 billion Olympic-sized swimming pools," Cheng explained.

The impact of this is an increase in water temperatures. According to the study, the global average sea surface temperature in 2023 showed a notable rise of 0.23 degrees Celsius compared to the previous year, 2022.

The study also calculated the salinity of ocean water, discovering that areas of high salinity experienced an increase in salinity, whereas the opposite was true for areas of lower salinity.

"The salty gets saltier, while the fresh gets fresher" pattern also ranked among the top five years.

Ocean warming will reduce oxygen in seawater and its ability to take up carbon dioxide, leading to severe consequences for ocean, plant and animal life, said the study.

It can also supercharge the weather. The extra heat and moisture that enters the atmosphere make storms more severe, with heavier rain, stronger winds, and more significant flooding.

According to the scientists, ocean warming is an irreversible phenomenon that will persist throughout this century, even if greenhouse gas emissions could be stopped.

"This poses new challenges for climate governance, requiring not only emission reduction and increased use of renewable energy sources but also a greater focus on climate change adaptation," said Cheng.

He called for strengthened climate monitoring capabilities and improved forecasting and early warning systems to prevent climatic disasters.