📄 earth_science

A physics-based framework for monitoring global temperature surges

This paper presents a physics-based monitoring framework that successfully explains global surface temperature variations using Earth's energy imbalance and El Niño-driven subsurface heat release, while projecting that a strong 1997/98-class El Niño could cause the 2023/24 record to be exceeded by 0.33 K.

Original authors: Shoshiro Minobe, Erik Behrens, Kirsten Findell, Erich Fischer, Benoît Meyssignac, Takuro Michibata, Rowan Sutton

Published 2026-08-07

📖 7 min read🧠 Deep dive

CC BY 4.0

Original authors: Shoshiro Minobe, Erik Behrens, Kirsten Findell, Erich Fischer, Benoît Meyssignac, Takuro Michibata, Rowan Sutton

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

The Planet's Fever and the Ocean's Thermostat

Imagine the Earth as a giant, living house. Sometimes, this house gets too hot, not just because the sun is shining brighter, but because the house is holding onto more heat than it lets out. Scientists call this "Earth's energy imbalance." It's like a bathtub where the faucet is running faster than the drain; the water level (heat) keeps rising. Usually, this happens slowly over decades, but recently, the water level has been spiking wildly.

To understand why, we need to look at two main characters in this story. First, there's the "faucet," which is the extra heat trapped by our atmosphere. Second, there's the "bathtub's secret compartment," the deep ocean. The ocean acts like a massive sponge. Sometimes, it soaks up extra heat from the surface and hides it deep down. Other times, it squeezes that heat back out, dumping it onto the surface and making the air above it feel much warmer. This squeezing and soaking is driven by a natural weather pattern in the Pacific Ocean called El Niño. When El Niño is strong, it's like someone suddenly opening a valve in the deep ocean, releasing a flood of stored heat into the atmosphere.

Why does this matter? Because when the air gets too hot, it causes storms, droughts, and melting ice. We need to know why the temperature is jumping up so we can predict what's coming next. Is it just the faucet running faster, or is the ocean suddenly dumping its secret stash? This is the puzzle a team of scientists set out to solve.

The Heat Budget: A Physics-Based Crystal Ball

A team of researchers has built a new "physics-based framework" to act like a financial ledger for the Earth's heat. Instead of just guessing why the planet is getting hotter, they created a system that tracks the money (energy) coming in and going out every single month. Their goal was to see if they could explain the recent record-breaking heatwaves and, more importantly, predict what the next year might look like.

The Ledger of the Atmosphere and Ocean
The scientists focused on a specific "near-surface" layer of the Earth: the air we breathe and the top 100 meters of the ocean. They call the total energy in this layer "A+O100." Think of this as the "active cash register" of the planet. To figure out how much money is in the register at any given time, they used a simple rule: What you have today = What you had a year ago + What came in this year - What went out.

In their equation, "What came in" is the Earth's energy imbalance (EEI)—the extra heat trapped by clouds and greenhouse gases. "What went out" is actually a bit tricky; it's the heat that gets sucked down into the deep ocean or released from the deep ocean. The team found that if you track the energy coming from the top of the atmosphere and the heat moving up and down in the tropical Pacific (specifically the 100–300 meter layer), you can explain almost all the changes in global temperature.

The "Aha!" Moment: Closing the Book
The researchers tested this framework using data from the "Argo era" (starting in 2005), a time when we have excellent global ocean measurements. They found that their "heat budget" closed perfectly. In other words, the math worked out every single month. When they compared their calculated energy levels to the actual observed global temperatures, the match was incredibly strong, with a correlation of 0.964. This means their model didn't just guess; it accurately reproduced the real-world temperature swings we've seen, including the massive surges in 2023 and 2024.

They identified four main players in this drama:

The Carryover: The heat left over from the previous year. This is the biggest factor. Once the planet gets hot, it tends to stay hot because that heat is "inherited."
The EEI Surge: The steady, rising amount of heat being trapped by the atmosphere. This is always positive and keeps getting stronger.
The Subsurface Release: The heat released from the deep tropical Pacific during an El Niño. This is the variable that causes the big spikes.
The Background Uptake: A steady, slow drain of heat into the deep ocean that happens all the time, acting as a constant cooling force.

Why the Recent Heat Was So Extreme
The paper explains that the record-breaking heat of 2023 and 2024 wasn't just one thing. It was a "perfect storm" where two drivers acted together. First, the Earth's energy imbalance (the trapped heat) surged to record levels, concentrated heavily near the equator. Second, a strong El Niño transitioned from a multi-year La Niña (which had been soaking up heat), forcing a massive amount of stored heat from the tropical Pacific subsurface up to the surface. The model shows that without the El Niño releasing this heat, the temperature spike wouldn't have been nearly as severe.

Looking Ahead: The 2026/27 Forecast
The most exciting part of the paper is the "outlook." The team used their framework to project what might happen over the next year, assuming a new El Niño is developing (which, according to NOAA, has an 81% chance of becoming very strong). They created three scenarios based on history:

The Small Release: Similar to the 2002/03 El Niño (15 ZJ of heat released).
The Medium Release: Similar to the 2009/10 El Niño (24 ZJ).
The Big Release: Similar to the legendary 1997/98 "Super El Niño" (48 ZJ).

The results suggest that even the "small" scenario would likely break the previous global temperature record. However, if the "Big Release" scenario plays out, the paper suggests the global temperature could surge by 0.33 K above the 2023/24 record. This would push the global temperature to 2.03 K above pre-industrial levels. The peak of this surge is predicted to happen in early 2027, specifically around February or March, depending on how strong the El Niño gets.

What the Model Rules Out
It's important to note what this framework says doesn't drive the temperature changes. The paper explicitly rules out the idea that the deep global ocean (below 100 meters) is the primary driver of these year-to-year spikes. When they tried using the deep ocean as their predictor, the math didn't work; the numbers were messy and didn't match the temperature records. The heat exchange is specifically happening in that shallow, tropical Pacific layer (100–300 meters).

How Sure Are They?
The authors are very confident in their ability to explain the past, with their model explaining 96% of the observed variance. For the future, they are cautious but clear. They state that their projections are based on "scenarios" and historical patterns, not a guaranteed crystal ball. The uncertainty grows as they look further ahead, ranging from ±0.07 K to ±0.11 K in their temperature predictions. They emphasize that the "carryover" of heat from 2026 will likely keep temperatures high regardless of the El Niño, but the size of the El Niño's heat release is the wild card that determines just how hot it gets.

In short, this paper gives us a new, physics-based way to watch the Earth's fever. It tells us that the recent heat spikes were a combination of a trapped heat surge and a massive release of ocean heat. Looking forward, it suggests we should brace for another record-breaking year in 2027, with the exact severity depending on how much heat the Pacific Ocean decides to let go.

Technical Summary: A Physics-Based Framework for Monitoring Global Temperature Surges

Problem Statement
Earth's climate has recently entered a period of exceptional extremes, with global surface temperatures in 2023 and 2024 breaking records by unusually large margins. These surges are driven by two concurrent physical mechanisms: the release of heat from the tropical-Pacific subsurface associated with the transition from multi-year La Niña to strong El Niño conditions, and a surge in Earth's Energy Imbalance (EEI) superimposed on a long-term positive trend. While previous studies have analyzed these mechanisms in the context of individual events, there is a lack of a continuous, physics-based framework that tracks the coupled evolution of EEI and vertical ocean heat exchange on a month-by-month basis to both attribute past changes and project future temperature trajectories.

Methodology
The authors propose a continuous, one-year heat budget framework for the near-surface climate system. The methodology is grounded in the conservation of energy over a one-year interval, where the change in total column energy equals the time-integrated net radiation at the top of the atmosphere (TOA).

Near-Surface Energy Definition: The framework isolates the near-surface energy ( $A + O_{100}$ ), defined as the sum of the global atmospheric energy anomaly ( $A$ ) and the global 0–100 m near-surface ocean heat content (OHC) anomaly ( $O_{100}$ ). This metric is shown to co-vary strongly with Global Mean Surface Air Temperature (GSAT) during the Argo era ( $r = 0.965$ ).
Budget Equation: The reconstruction of $(A + O_{100})$ $(A + O_{100})$ for any target month $t$ $t$ is expressed using four terms derived from the preceding year:
- Carryover: The observed value of $(A + O_{100})$ from one year prior, $(A + O_{100})(t - 1\text{yr})$ .
- Integrated EEI: The trailing one-year integral of Earth's Energy Imbalance ( $\int R dt$ ).
- Subsurface Heat Exchange ( $S$ ): The one-year change in subsurface ocean heat storage, specifically defined as $S = -\Delta_{1\text{yr}}(O_{sub})$ . The authors identify the tropical-Pacific 100–300 m layer as the optimal subsurface reservoir, as it captures ENSO-driven vertical heat exchange and avoids the product-dependent trends found in deeper global layers.
- Background Uptake ( $C$ ): A constant term representing the steady heat uptake by the deeper ocean, land, and cryosphere, treated as a constant ( $12.4 \text{ ZJ yr}^{-1}$ ).
Data Sources: The analysis utilizes monthly data from January 2005 onward (the start of near-global Argo sampling). Inputs include CERES-EBAF for TOA radiation, three independent OHC products (ORAS5, EN4, IAP), and ERA5 for atmospheric energy.
Projection Scenarios: For the outlook component, the framework projects $(A + O_{100})$ one year ahead by combining the current near-surface energy, a linear trend projection of future EEI, and three scenario-based trajectories for subsurface heat release ( $S$ ) derived from historical El Niño events since 1995 (smallest, median, and largest releases).

Key Results

Budget Closure: The framework successfully closes the one-year heat budget month-by-month throughout the Argo era (January 2006–present). The reconstruction of $(A + O_{100})$ reproduces observed values with a correlation of 0.986 and a root-mean-square error (RMSE) of 4.5 ZJ, explaining 96% of the observed variance. When converted to GSAT, the correlation is 0.964 with an RMSE of 0.068 K.
Attribution of Recent Extremes: The analysis attributes the exceptional warmth of 2023/24 to the carryover of heat from the previous year, a rising integrated EEI, and a strong positive subsurface heat release term ( $S$ ) during the El Niño. Conversely, the decline in near-surface energy observed in 2024 and 2025 is attributed primarily to the subsurface ocean taking up heat (negative $S$ ) during the subsequent La Niña phase, which acts as the only process capable of substantially cooling the near-surface system on a year-to-year timescale once a surge has developed.
Spatial Distribution: The elevated net radiation driving these surges is concentrated at low latitudes. The 30°S–30°N belt accounts for 80% of the global-mean EEI anomaly in 2022/23 and 87% in 2025/26. This anomaly is dominated by reduced shortwave reflection, primarily from clouds.
Future Outlook: Based on a developing El Niño declared in June 2026, the framework projects three potential trajectories for the coming year. Even under the smallest release scenario (15 ZJ, comparable to 2002/03), the projected GSAT would match or exceed the previous record. A median release (24 ZJ) and a "1997/98-class" release (48 ZJ) would result in GSAT peaks of 1.79 K and 2.03 K above the 1850–1900 pre-industrial baseline, respectively. The 1997/98-class scenario suggests a potential record break of 0.33 K above the 2023/24 record.

Significance and Claims
The paper claims to provide the first continuous, physics-based monitoring framework that links Earth's energy imbalance and El Niño-driven subsurface heat exchange to global surface temperature variations on a monthly basis. By demonstrating that the budget closes consistently over the Argo era, the study validates the hypothesis that near-surface energy levels are governed by accumulated EEI, tropical-Pacific subsurface heat exchange, and a steady background uptake.

The significance of this work lies in its dual output:

Attribution: It offers a quantitative explanation for past temperature changes, distinguishing between the roles of radiative forcing (EEI) and internal variability (ENSO heat exchange).
Outlook: It provides a scenario-based projection for the coming year's global surface temperature, explicitly incorporating the observed rise in EEI and potential magnitudes of El Niño heat release.

The authors assert that regularly updating this framework (e.g., in annual climate assessments) would advance the understanding and prediction of global temperature variations driven by these two primary physical mechanisms. The study does not claim to predict specific weather events but rather the thermodynamic evolution of the global climate system over a one-year horizon.

The Planet's Fever and the Ocean's Thermostat

The Heat Budget: A Physics-Based Crystal Ball

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