A record-breaking 23 zettajoules of heat was sunk into the world's seas last year, leaving ocean waters hotter and higher, a report has found.
The addition of thermal energy was almost 40 times greater than all the energy humanity used over the same period.
Sea levels have risen by about 3.8mm a year since 1999, and at a faster rate of 4.2mm a year between 2012 and 2025, according to the tenth edition of the Copernicus ocean state report. It found that the global ocean has become 17 per cent more acidic over the last 40 years.
The oceans have absorbed about a third of the carbon dioxide humanity has emitted, and about 90 per cent of the extra heat that greenhouse gases have trapped in the Earth's system.
"The ocean is transforming before our eyes," said Pierre Bahurel, director general of Mercator Ocean International, which published the report. "Warming, rising seas and ecosystem degradation are interconnected signs of significant and long-term change."
In Europe, which is heating twice as fast as the global average, the Mediterranean and Black Seas have seen record-breaking marine heatwaves, with elevated temperatures persisting deep below the surface and bouts of extreme heat lasting more than a month.
The scientists found a clear acceleration of sea level rise in the western Mediterranean, while the eastern part showed uneven gains. The sea as a whole has warmed by 0.32C per decade.
The units deserve a moment. A joule is the amount of electricity required to run a one-watt device for one second. A zettajoule is a billion trillion joules. Twenty-three of them is the figure for a single year.
All of which is ordinary climate science, reported in the ordinary way. It is also, read strictly, an energy-consumption statistic, and this newspaper would like to see it filed as one.
Energy in that quantity is normally attributed to a consumer. On the report's figures the ocean took in almost forty times the annual draw of every household, vehicle, factory, data centre and power station on Earth combined. It is, by a margin no other entity approaches, the planet's dominant energy user.
Its position within the system is equally striking. The ocean also absorbed roughly 90 per cent of the surplus heat trapped by greenhouse gases, which in any other sector would be classed as waste recovery, and would attract a subsidy.
Yet the ocean holds no connection agreement, has filed no consumption return in ten editions of the report, and publishes no efficiency target. It has been approached about demand-side response and has not replied.
Its consumption is not even flat. Sea level rise has gone from 3.8mm a year to 4.2mm a year, and the Mediterranean is warming at 0.32C a decade, which is the behaviour of a customer steadily increasing its load without notifying anybody.
The Department of Unnecessary Research has therefore written to the ocean to request a meter reading. It accepts that the ocean covers most of the planet and may consider itself exempt, but notes that this is precisely the argument the largest consumers always make.