Facebookhttps://www.facebook.com/share/p/1Fz7JAoznf/The rate of the Earth Energy Imbalance (EEI) increase and global Ocean Heat Content (OHC) increase (mostly to deep into the uppermost 2000 meter layer) more than doubled starting in ~2017 and is related to the strong El Niño (EN) of 2015-2016. With the 2026-2027 EN looking like it will be stronger by a large margin, the inference is that this could lead to a sharp additional rise in the rate of global OHC increase and of the EEI around 2028. If that is the case then a larger average global 2 m height air temperature increase is already baked in unless we drastically and very rapidly reduce greenhouse gas emissions and existing atmospheric concentrations.
The sharp increase and subsequent acceleration in global OHC starting in ~2017 is primarily driven by accelerating atmospheric greenhouse gas concentrations and the accumulation of Earth's excess thermal energy deep within the ocean layers. Because the world's oceans absorb more than 90% of the excess heat trapped by greenhouse gases, full-depth OHC acts as the primary indicator of global warming, experiencing less year-to-year fluctuation from temporary weather events than surface temperatures do.
Scientists point to several overlapping factors that explain the distinct surge around 2017:
1. The planet experienced one of the most powerful El Niño events on record between 2015 and 2016. During an El Niño, vast amounts of ocean heat are released into the atmosphere, causing atmospheric surface temperatures to spike. Once that cycle ended, the ocean surface cooled slightly, but the ongoing global energy imbalance meant the oceans immediately resumed absorbing massive amounts of heat. Instead of staying at the surface, this heat was mixed and stored deep into the 0–2000 meter layers.
2. According to findings published by the Institute of Atmospheric Physics (IAP), the sharp spike in 2017 was not uniform across the planet. An unusually massive amount of thermal energy was deposited into the Atlantic Ocean and the Southern Ocean, pushing full OHC to record-breaking thresholds—absorbing an extra 1.51 x 10^22 Joules compared to previous baselines.
3. Data from the National Oceanic and Atmospheric Administration (NOAA) confirmed that 2017 saw atmospheric carbon dioxide concentrations hit 405 parts per million (ppm), which was the highest in modern recorded history. Currently it is 427 to 429 ppm. As these gases trap more energy, Earth’s energy imbalance worsens, forcing the oceans to continually uptake greater quantities of heat at a much faster rate.
4. According to data tracked by NASA’s Estimating the Circulation and Climate of the Ocean (ECCO), the upper 200 meters of the ocean saw a pronounced acceleration in heat content right after 2017. This acceleration means that the ocean is warming more than twice as fast over the last decade compared to previous decades.
Because water has a much higher heat capacity than air (the oceans have a total heat capacity about 1,000 times that of the atmosphere) the oceans act as Earth's primary climate buffer.
In 2025, ocean heat content (OHC) set yet another consecutive record high, storing an immense volume of energy.
The oceans absorb about 90% of the EEI while EEI is accelerating. While the total amount of heat the ocean absorbs is skyrocketing - because the total EEI is accelerating - the 90% share is projected to remain relatively stable in the near future, though subtle shifts are possible.
The absolute velocity of heat absorption is accelerating. Due to rising greenhouse gases and declining global reflectivity (albedo) from melting ice and fewer marine clouds, the Earth's total energy imbalance has dramatically widened. 👉The rate of ocean warming has effectively quadrupled over the past four decades.👈
As the top layer of the ocean warms, it becomes less dense than the cold water beneath it, leading to increased stratification (layering). This makes it harder for the ocean to mix. If the warm surface layer cannot efficiently transport heat down into the deep ocean, the surface layer will heat up even faster. Over a long timeframe, this could decrease the ocean’s efficiency as a heat sink, leaving a slightly higher fraction of heat to remain in the atmosphere and accelerate land warming.
Large -scale ocean currents like the AMOC act as a conveyor belt that pushes heat into the deep ocean. Climate models indicate that as fresh meltwater from glaciers flows into the sea, the AMOC may weaken. A weaker conveyor belt alters regional heat uptake patterns and reduces how effectively the deep ocean stores excess energy.
While the ocean’s heat absorption remains high, its carbon dioxide absorption is a different story. The ocean absorbs about 25–30% of human-emitted CO2. However, warmer water physically holds less dissolved gas. Scientists have observed that the ocean’s carbon sink capacity is showing signs of weakening during extreme heat years. If the ocean absorbs less CO2, atmospheric CO2 will rise faster, widening the EEI and forcing the ocean to absorb even more heat.
More:
https://ecco-group.org/ohc.htm