Climate: The oceans absorbed enough energy in 2023 to boil "billions of Olympic swimming pools"

Europe 1 with AFP / Photo credit: Handout / GETTY IMAGES NORTH AMERICA / Getty Images via AFP 16:36 p.m. on January 11, 2024

The oceans, which store most of the excess heat caused by our greenhouse gas emissions, still absorbed a colossal amount of energy in 2023, equivalent to that needed to boil "billions of Olympic swimming pools", according to a baseline study on Thursday. Through feedback, part of the immense energy contained in the seas contributed to warming the atmosphere and making 2023 the hottest year in history, with its procession of climate disasters, recalls this synthesis published in the journal Advances in Atmospheric Sciences by 19 researchers, notably from American, Chinese and Italian universities.

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The oceans, which cover 70% of the planet's surface, are a major regulator of the Earth's climate since they absorb about 90% of the excess heat caused by human activity. In turn, "a warmer ocean leads to a warmer and wetter atmosphere, with more unpredictable weather," the journal's statement said.

A crucial indicator for global warming observers

In 2023, the total heat contained in the oceans between the surface and 2,000 meters deep reached a new record, with the addition of about 9 or 15 zettajoules compared to 2022, according to the respective estimates of the American Atmospheric and Oceanic Administration (NOAA) and the Chinese Institute of Atmospheric Physics (IAP) unveiled by the study. A zettajoule is one joule, a unit of measurement for energy, with 21 zeros behind it. "Every year, the whole world consumes about half a zettajoule of energy to power our economies. In other words, 15 zettajoules is enough energy to boil 2.3 billion Olympic-sized swimming pools," the statement said.

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The energy contained in the oceans is a crucial indicator for observers of global warming, as it is less affected by natural climate variability than ocean surface temperatures. The latter have been breaking seasonal records since April, under the long-term effect of this excess heat accumulated at depth, but also the return in 2023 of a strong episode of the natural climate phenomenon El Niño, expected to reach its peak in early 2024 in the Pacific Ocean.

This warming of the seas leads to an increase in the salinity of the water and the stratification (the separation of water into different layers) of the oceans, which alters the exchange of heat, carbon and oxygen between the oceans and the atmosphere. In turn, these phenomena can alter the currents, on which the weather depends, but also reduce oxygen in the water and threaten marine life, as well as reduce the absorption capacity of our greenhouse gas emissions in the seas.