Our home planet is struggling with a record energy imbalance, which is warming oceans to unprecedented levels, making weather more extreme and threatening health and food supplies, the World Meteorological Organization has warned.
The United Nations body confirmed 2015 to 2025 were the hottest 11 years ever measured, but a still bleaker message was that the rising temperature experienced by humans on the surface was only 1% of the faster-accumulating heat in the wider Earth system.
More than 90% of that excess is absorbed by the oceans, which experienced the highest heat content in history last year. The rate of ocean warming has more than doubled over the past two decades, compared with the average over the previous 45 years.
The authors of the latest annual State of the Global Climate report say this highlights the increasing vulnerability of a planet that is moving ever further out of balance as a result of human activity. The burning of oil, gas, coal and forests releases heat-trapping greenhouse gases such as carbon dioxide, methane and nitrous oxide, which are all at their highest level in at least 800,000 years.
This disrupts the planet’s energy equilibrium. In a well-functioning system, the amount of radiation entering and leaving the Earth system is roughly similar. But a heat surplus has been accumulating since at least 1960 and has noticeably accelerated in recent years.
This is tracked for the first time in the new report, which shows the Earth’s energy imbalance increased by about 11 zettajoules a year between 2005 and 2025, which is equivalent to about 18 times total human energy use. Last year it was more than double that average.
At present, humans and other life forms on the surface directly suffer only a small fraction of that energy backup because 91% is absorbed by oceans, 5% by the land, 1% warms the atmosphere, and 3% melts ice at the poles and on high mountains.
But even with only a tiny share of this extra energy, the world’s surface temperatures – which are the most commonly used measure of global heating – are climbing to alarming levels. Last year was the second- or third-hottest on record, depending on the dataset. World leaders say it is now inevitable the planet will – at least temporarily – breach the target of limiting heating to 1.5C above preindustrial levels set by the Paris agreement. They say the dire consequences are already evident in faltering harvests, worsening dengue outbreaks and increasingly severe heatwaves, forest fires and storms.
“The state of the global climate is in a state of emergency. Planet Earth is being pushed beyond its limits. Every key climate indicator is flashing red,” said the UN secretary-general, António Guterres. “Humanity has just endured the 11 hottest years on record. When history repeats itself 11 times, it is no longer a coincidence. It is a call to act.”
The effect on the oceans is still not fully understood, but the impacts are expected to be still more profound and long-lasting. Sea levels are rising at an accelerating pace, and sea ice is at its third-lowest level ever.
The authors of the paper said more of the heat is moving into the depths, which is affecting circulation and locking in the consequences for thousands of years.
Nearer the surface, heatwaves and acidification are a growing problem for corals and other marine life, while the melting of ice is pushing up sea levels and weakening the planet’s ability to reflect solar radiation back into space, thus adding to the energy imbalance.
There is no respite in sight. The Pacific is coming to the end of a La Niña phase, which is usually associated with cooler temperatures at the surface across much of the world. By the end of this year, forecasts suggest this could be replaced by an El Niño, which will bring more heating. “If we transition to El Niño we will see an increase in global temperature again and potentially to record levels,” said Dr John Kennedy, the lead author of the WMO report.
