The world’s oceans were the hottest ever recorded in 2022, indicating the profound and pervasive changes that human-caused emissions have made to the planet’s climate.
More than 90% of the excess heat trapped by greenhouse gas emissions is absorbed by the oceans.
Sea surface temperatures are a major influence on the Earth’s weather. Hotter oceans supercharge extreme weather, causing more intense hurricanes and typhoons and more moisture in the air, which brings more intense rains and flooding. Warmer water also expands, raising sea levels.
The temperature of the oceans is far less affected by natural climate variability than the temperature of the atmosphere, making the oceans a much better indicator of global heating.
Reliable ocean temperature measurements go back to 1940 but it is likely the oceans are now at their hottest for 1,000 years and heating faster than any time in the last 2,000 years.
The oceans absorbed roughly 10 zettajoules more heat in 2022 than in 2021, equivalent to every person on Earth running 40 hairdryers all day, every day.
The researchers also analyzed salinity, which along with temperature determines water density and is a crucial driver of ocean circulation. An index of the variability in salinity across the oceans reached a new high in 2022.
Another important feature of the oceans is stratification, where the layering of water by density becomes amplified. One consequence of this is that less mixing in the ocean means the surface layer absorbs less carbon dioxide from the atmosphere, increasing global warming.
The warming of the oceans, and the impacts on extreme weather, will increase until humanity reaches net zero emissions.