The Hydra is a creature from Greek mythology—famously the Lernaean Hydra, a serpentine water monster with multiple heads. Its most well-known characteristic is its ability to grow two new heads for every one that is cut off. Likewise, no matter how much we progress in our knowledge of the universe, misinformation seems always to “grow another head.”
The latest example confronting me in the knowledgesphere is a theory promoted by Gregg Braden, a popular author and speaker in the New Spirituality and “science and mystery” genre. Braden proposes that the primary driver of ocean warming is not atmospheric greenhouse gases but heat emanating from within the Earth itself.
Gregg Braden is a five-time New York Times best-selling author, scientist, and educator. He is known as a pioneer in the emerging paradigm that blends science, social policy, and human potential. His work explores how ancient traditions and modern science can converge, focusing on topics like intuition, healing, and consciousness.
His following includes people interested in these themes, and his work has been influential for individuals seeking personal transformation and a deeper understanding of human potential. He has a significant presence on social media, with almost a million subscribers on his official YouTube channel, and his videos regularly receive over 100 000 views.
Braden’s notable works include "The Divine Matrix", "The Spontaneous Healing of Belief", "Human by Design", and "The Wisdom Codes". His books have been published in over 40 languages, and he has given presentations in more than 30 countries. He has also been invited to speak at organisations such as the United Nations, Fortune 500 companies, and the US military. His followers often praise his ability to connect neuroscience, quantum physics, and biology with spirituality and ancient wisdom, offering a new perspective on human nature and its potential.
If you are not troubled that someone who denies anthropogenic climate change, evolution and much of modern medicine has such reach into people’s minds, then perhaps you are simply crossing your fingers and hoping for the best.
Braden’s hypothesis has enough surface plausibility to confound the average viewer. Heat from geological activity is indeed substantial—global geothermal flux is roughly 47 terawatts, of which about 10 TW emerges beneath the oceans. Braden asserts that undersea geothermal activity is responsible for ocean warming.
On the face of it, this might seem possible. Heat released from undersea thermal vents encounters cold water almost immediately and loses its heat to the surrounding sea before it can reach the surface. On the other hand, heat from above the surface penetrates only the top few metres of the ocean. You can sense this when you dive into a mountain waterhole on a hot day: the water at the surface may be a comfortable 22 °C, but only centimetres below it is uncomfortably cold, perhaps 10 °C.
This phenomenon, known as thermal stratification, occurs when a body of water forms layers of different temperatures. Warm water, being less dense, stays on the surface, while the cold water below remains at a low temperature, often influenced by its source, such as a cold underground spring or snowmelt.
The boundary between these layers is called a thermocline. When you dive or move your hand just a few centimetres below the surface, you cross this thermocline and enter significantly colder water. At first glance, this might make it seem more plausible that the ocean is warming from below than from above.
We therefore appear to face a conundrum that could challenge our understanding of global warming, particularly in the oceans. Is Braden simply providing an “update” on science? His disciples certainly claim that this physical reality is a death blow to the assertion that ocean warming is caused by anthropogenic climate change.
Complicating the idea that oceans can absorb heat from above is another feature of water: it does not easily mix with water of different temperature, salinity or turbulence. Layers or streams of water can be found worldwide where the barrier between fresh and saline or warm and cold water seems almost insurmountable. Even in the pipes of a house, flows may be laminar or turbulent depending on velocity, viscosity and the geometry of the path. Water simply does not like mixing with other water; the fact that you stir your tea illustrates the need for added energy to induce mixing.
How, then, can heat from above the oceans change the ocean temperature?
Before answering, we can note a simple fact that undermines Braden’s claim—a “low-hanging fruit,” as it were. Despite the seemingly enormous amount of heat from geothermal sources, it is tiny compared with the energy arriving from the Sun. Although our mapping of undersea thermal vents is incomplete, even the 65 000 km-long Global Mid-Ocean Ridge probably hosts only a few thousand vents.
The Sun delivers about 173 000 terawatts of energy to the Earth’s atmosphere and surface. Geothermal heat totals about 47 TW globally (roughly 10 TW to the oceans). For geothermal energy to match the rise in ocean temperature attributed to solar heating and greenhouse gases, about 20 000 times more hydrothermal vents would need to have appeared in the past century—something geologists know does not happen. Geological activity changes over millions of years, not mere centuries.
Braden’s hypothesis therefore fails to account for well-established geological evidence.
Furthermore, the clear difference between ocean temperatures at the poles and at the equator provides an easy refutation. If ocean warming were driven mainly by geothermal activity, one would expect elevated temperatures to correlate with areas of high geological activity—yet polar regions would not be markedly colder. But they are.
So how do the oceans warm, and why is there such a temperature difference between poles and equator? Grade 8 science—the water cycle—offers the answer. The water cycle is essentially an energy cycle: water is a medium for transporting energy.
At the equator, solar radiation heats the surface of the water, causing evaporation. Moisture accumulates in the air until it is saturated and then rain falls. Although the rain loses some heat, because of water’s high heat capacity much of the rain remains warmer than the ocean’s average temperature even if it feels cooler than the air. We feel relief after rain on a hot day because the air cools.
At the poles, the lack of solar radiation means little surface heating, so ocean temperatures can drop below freezing while at the equator they stay around 30 °C. These temperature differences create currents that efficiently transport warm water to colder regions—for example, the Gulf Stream.
Between solar radiation and these powerful currents—the ocean’s stirring mechanism—and despite water’s natural resistance to change, heat is distributed throughout the ocean.
Braden’s hypothesis, therefore, is effectively refuted.
Geothermal Myth of Ocean Warming
Why solar energy and established ocean science decisively outweigh Gregg Braden’s undersea heat hypothesis.
Gregg Braden’s claim that undersea geothermal heat drives ocean warming collapses when compared to the overwhelming influence of solar radiation and the well-understood dynamics of ocean mixing and currents.