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A post shared by a user on social media claims that ocean currents and water vapour are far more important than carbon dioxide in shaping Earth’s climate. The post argues that because oceans store most of the planet’s heat and water vapour is a stronger greenhouse gas, it “makes little sense” to attribute global climate to CO2, which it describes as only a trace gas in the atmosphere.
The post does include some real facts about ocean circulation and heat storage, but it uses them to draw a misleading conclusion. Climate science shows that ocean currents help move heat around the planet and water vapour helps amplify warming, but neither of them cancels out the role of long-lived greenhouse gases. Assessments from the IPCC, WMO, and other climate institutions continue to identify rising CO2 from human activity as the main driver of today’s warming.
Claim post:
Claim 1: “It makes little sense to attribute global climate to a trace gas CO2, which is 420 ppm, or 0.042% of the atmosphere.”
Fact: False. CO2’s influence on climate does not depend on how much of the atmosphere it occupies, but on how effectively it traps heat. The IPCC’s Sixth Assessment Report explains that rising greenhouse gas concentrations change Earth’s radiative forcing, meaning they alter how much heat escapes to space. NOAA’s Annual Greenhouse Gas Index also shows that CO2 is the largest contributor to the increase in warming influence from long-lived greenhouse gases since 1990.
The “trace gas” framing leaves out the part that matters most: CO2 has risen sharply because of human activity, and even relatively small changes in its concentration can shift the planet’s energy balance. According to the World Meteorological Organisation, atmospheric CO2 increased from around 278 ppm in 1750 to 420 ppm in 2023, a rise of about 51%, and this increase is warming the planet.
Claim 2: “Water vapour is at least 100 times more influential for heat retention, particularly in tropical areas where it provides up to 75% of regional warming capacity.”
Fact: Misleading. Water vapour is indeed a powerful greenhouse gas, but it is not the main trigger of the warming we are seeing today. The UCAR Centre for Science Education explains that greenhouse warming strengthens when more heat-trapping gases are added to the atmosphere, while water vapour increases mainly in response to temperature. That is why climate scientists treat water vapour primarily as a feedback, not the initial forcing.
This distinction matters because water vapour does not build up independently in the way CO2 does. It cycles rapidly through evaporation, condensation, and rainfall, which means its atmospheric concentration is largely controlled by how warm the air already is. The IPCC identifies water vapour feedback as one of the key processes that amplifies greenhouse gas-driven warming, not a substitute for it.
Claim 3: “The oceans are key to the world’s variable climate. They contain 91-93% of all retained heat energy…” / “While the atmosphere changes by the day, the oceans provide the thermal memory of the planet.”
Fact: Misleading. The oceans do absorb most of the excess heat building up in the climate system, but that does not mean they are the root cause of the warming. NOAA’s National Centres for Environmental Information states that the ocean absorbs more than 90% of the excess heat, and NOAA notes that this heat is trapped in Earth’s system because of human-caused global warming.
So while the phrase “thermal memory” is broadly fair, it is being used here to imply the wrong cause. The ocean is acting as a storage reservoir for excess energy, not as an independent explanation that replaces greenhouse gases. In fact, the steady rise in ocean heat content is one of the clearest scientific signals that the planet is accumulating extra heat.
Claim 4: “They are the eternal thermal engines that drive climate variability around the world.” / “The two key currents are the Gulf Stream (Atlantic) and the Kuroshio (Pacific), and they transport heat poleward, influencing the global climate.”
Fact: Misleading. Ocean currents do play a major role in redistributing heat and shaping regional climate patterns. NOAA explains that ocean currents regulate global climate by moving warm water toward the poles and colder water back toward the tropics, helping balance the uneven distribution of solar heating across Earth’s surface.
But redistributing heat is not the same thing as causing the planet to gain more heat overall. The IPCC and NOAA both make clear that the long-term warming trend is being driven by an energy imbalance, where more energy is being retained in the Earth system than is escaping to space. Ocean currents can move that heat around, but they do not explain why there is more of it in the first place.
Claim 5: “The Earth’s great ocean currents have carried warm waters up from the tropics to Northern Europe for hundreds of millions of years.” / “This prevents most of Europe from freezing in a climate similar to Greenland.”
Fact: Misleading. There is a real scientific basis to the idea that ocean circulation helps keep parts of Europe milder than some other regions at similar latitude. The UK Met Office-led study explains that heat transported into the North Atlantic helps make the UK and nearby parts of Europe warmer than they would otherwise be, and that the Gulf Stream is part of the wider Atlantic Meridional Overturning Circulation.
But this does not weaken the evidence for greenhouse warming. A real influence on regional climate does not disprove the role of CO2 in global climate change. The question in modern climate science is not whether ocean currents exist, but why the entire Earth system, including the atmosphere and ocean, is gaining excess heat over time. That answer still points to rising greenhouse gases.
What does the science actually show?
Peter Clack’s post works by combining accurate pieces of ocean science with a misleading conclusion about what drives climate change. Oceans matter deeply to the climate system, and water vapour is a major part of the greenhouse effect, but neither of those facts overturns the evidence linking rising CO2 to modern warming.
The broader scientific record shows a consistent picture. Greenhouse gas concentrations are rising, Earth’s energy imbalance has increased, the oceans have stored most of the excess heat, and global temperatures continue to rise in step with these changes. Taken together, these observations do not support the post’s argument. They support the mainstream scientific understanding of human-driven climate change.
References:
https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-7
https://gml.noaa.gov/aggi/aggi.html
https://wmo.int/news/media-centre/2024-track-be-hottest-year-record-warming-temporarily-hits-15degc
https://scied.ucar.edu/learning-zone/how-climate-works/greenhouse-effect
https://www.ncei.noaa.gov/news/ocean-heat-content-rises
https://www.climate.gov/news-features/understanding-climate/climate-change-ocean-heat-content
How does the ocean affect climate and weather on land?
Banner image: Photo by Viktor Lysenko on Unsplash
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