From Watts Up With That?

By Anthony Watts

There are mistakes, and then there are mistakes that only happen when you already know the answer you want.

The newly published paper “Ocean Heat Content Sets Another Record in 2025” reports a year-to-year increase in upper-2000-meter ocean heat content of about 23 zettajoules (ZJ), depending on dataset. Fine. Ocean heat content (OHC) is a possible diagnostic metric, and most people studying the Oceans believe that the oceans have been warming since the end of the Little Ice Age. However, as we recently pointed out in the WUWT post “Measuring Climate Change Without a Ruler,” from a strict epistemological standpoint, we do not know—at high confidence—whether the total energy of the Earth’s climate system is increasing, decreasing, or remaining approximately constant.

But then came the Twitter/X post — and this is where physics quietly left the room, and narrative building took its place.

Zeke Hausfather, a coauthor, triumphantly announced:

In a newly published paper, we find that in 2025 human emissions of greenhouse gases added around 23 billion trillion joules of heat to the world's oceans – 39 times as much as the annual energy produced by all human activity on Earth. https://t.co/tJISNHNkpO pic.twitter.com/WzroYGug3s

— Zeke Hausfather (@hausfath) January 13, 2026

This is not a harmless simplification. It is flatly wrong — and it is wrong in a way that a supposedly competent “climate scientist” absolutely should know better than to make. He’s attributing the increased energy retention solely to a single variable – Carbon Dioxide. Earth’s climate system is far more complex than that.

What happened here is not a math error. It is confirmation bias, plain and simple: starting with the conclusion (“GHGs did it”) and backfilling the interpretation, even if it violates basic energy accounting.

Let’s walk through it slowly, because apparently that’s necessary.

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What the paper actually says (and what it very carefully does not.) The paper is here.

The paper reports that global upper-2000 m ocean heat content increased by ~23 ± 8 ZJ from 2024 to 2025 in one dataset (IAP/CAS), with smaller increases in others.

That number is:

• an observed year-to-year change
• a net storage term
• the residual of everything that happened to the climate system that year

It already includes:

• greenhouse gas forcing (from all prior years, not just 2025),
• aerosol changes,
• ENSO evolution (the paper explicitly mentions La Niña development),
• atmosphere–ocean heat exchange,
• internal variability,
• circulation and mixing,
• and, yes, measurement uncertainty.

It is the entire balance sheet, not a line item. Nowhere does the paper calculate:

• heat from 2025 emissions,
• a partition of OHC change by forcing agent,
• or an attribution showing that GHGs alone account for 23 ZJ.

Because it can’t — at least not from this analysis.

As the great Steve McIntyre is fond of saying, “Watch the pea under the thimble.”

Hausfather’s tweet commits a textbook category error.

It takes:

• a change in stored energy (ΔOHC, a stock),

and rebrands it as:

• heat added by that year’s emissions (a flow).

This is Climate Science 101 stuff. You don’t get to do this. By that logic, one could just as easily say:

• “In 1998, CO₂ emissions caused El Niño,”
• or “In 2023, SUVs caused the Pacific Decadal Oscillation.”

Correlation plus narrative is not causation — especially when you skip the accounting.

It’s a basic conservation-of-energy test (which the tweet fails.)

Let’s take the claim literally.

If “2025 human emissions added 23 ZJ to the oceans”, then one of the following must be true:

1. Every other process affecting ocean heat that year added zero net energy, or
2. Some other process removed an equal and opposite amount of heat — and we can quantify it.

Neither is shown. Neither is even attempted. Instead, the tweet simply assigns 100% of the observed net heat gain to one favored cause. That’s not attribution. That’s myopic storytelling. Whether he meant cumulative emissions over time and phrased it badly, or he really believes the increase of CO₂ added all that extra heat is unclear. What is clear is that one year of increased emissions could not have added all that extra OHC.

Here’s the incremental forcing problem with the math shown. This is the part that completely breaks Zeke’s claim.

Atmospheric CO₂ increased by roughly 2–3 ppm during 2025 (consistent with CO2 global means).

Radiative forcing from CO₂ is commonly approximated as:

Taking a representative case:

That is the incremental forcing added in that year.

Now convert that forcing into energy over one year:

That is:

• 0.43 zettajoules (ZJ)

Not 23 ZJ.
Not even close Zeke. Maybe Zeke should create his own heat units. I propose Zekajoules – a fictional unit. That way, he’s never wrong.

Even allowing for generous assumptions, the incremental effect of 2025 emissions is well under 1 ZJ, not tens of ZJ. The climate system responds to the accumulated forcing from decades of emissions, not to the incremental bump from one year’s emissions — which is exactly why pretending that “2025 emissions added 23 ZJ” is nonsense.

This is the difference between forcing and storage, and confusing the two is inexcusable for a professional “climate scientist.”

ENSO, Zeke’s inconvenient elephant in the room.

The paper itself notes that evolving La Niña conditions likely contributed to the 2025 OHC change. ENSO redistributes tens of zettajoules of heat between ocean layers and the atmosphere on annual timescales. This is not controversial. It’s in the textbooks. Yet in the Zeke version of events, ENSO mysteriously vanishes — because it’s inconvenient to the preferred narrative. That’s confirmation bias at work.

Why this matters (and why this deserves calling out.)

Zeke Hausfather is not a random blogger. He is routinely presented as a serious “climate scientist,” cited by media outlets as a trusted explainer. That makes this worse, not better.

A graduate student might be forgiven for confusing:

Observed OHC change with heat attributable to a specific year’s emissions.

A published “climate scientist” should not. When a scientist allows narrative alignment to override physical meaning — especially in public communication — that’s not “simplifying for the public.” That’s lowering standards. And it wrongly trains journalists, policymakers, and the public to think energy accounting is optional.

It isn’t. But that’s the common narrative from “climate science” these days. Sigh.

What Zeke should have said:

Here’s a version of his Tweet that would have been technically correct, and without the biased and ambiguous language, nor placing blame on a single climate variable that is one of many in a complex climate system:

“Global upper-2000 m ocean heat content increased by ~23 ZJ from 2024 to 2025, reflecting the ongoing long-term planetary energy imbalance plus year-to-year variability, including ENSO evolution.”

That’s accurate.
That’s defensible.
That doesn’t require abusing units.

But it doesn’t make for a good viral climate scary tweet, does it?

The public is told to “trust the science.” But science only deserves trust when scientists:

• respect definitions,
• respect conservation laws,
• and resist the temptation to turn diagnostics into propaganda.

When a “climate scientist” takes a perfectly valid observational number and repackages it as “heat added by emissions” — without doing the attribution — that’s not science communication.

That’s confirmation bias with a PhD.

And non-PhD. people like me that are tired of this shit, notice.