The France Counterfactual

A Method for Quantifying Avoidable, but not Avoided, CO₂ Emissions, 1978–2025

1. What This Analysis Is

This paper lays out a simple, reproducible counterfactual: how much carbon dioxide would five major economies have avoided emitting between 1978 and 2025 had each decarbonized its energy supply at the rate France actually achieved?

France is not a hypothetical. Between 1978 and 1988 it cut the CO₂ intensity of its energy supply from roughly 65 to 41 Mt CO₂ per exajoule — a 37% reduction in a single decade — by executing the Messmer plan’s nuclear build-out.[1] No other large economy has ever decarbonized its energy supply that fast, before or since. That makes France’s trajectory the most demanding demonstrated benchmark available: not a model projection, not a policy aspiration, but a path a G7 economy actually walked, on 1970s technology, in about the time it now takes to permit a transmission line.

The analysis compares five economies against that benchmark: the United States, the European Union, Japan, South Korea, and Australia. For each country and each year, it asks one question: if this country’s energy supply had been exactly as carbon-intensive as France’s that year — while consuming exactly the energy it actually consumed — how much less CO₂ would it have emitted? The answer, summed over 48 years, is the price of the road not taken.

With technology available in 1978, at a pace France actually demonstrated, five other Western-aligned economies — the US, EU, Japan, South Korea, and Australia — could have avoided 184.9 Gt of CO₂ emissions between 1978 and 2025.

Two design choices define the method, and both are deliberately conservative. First, the counterfactual swaps only carbon intensity, never energy consumption. No country is asked to use less energy, grow more slowly, or change its industrial structure. Second, the benchmark is France’s actual intensity in each year, including its stumbles — the post-2020 reactor-availability dip is in the data. This is not a comparison against perfection; it is a comparison against a peer.

2. The Two Inputs

The entire analysis is built from two data series, both taken from a single source: the Energy Institute’s Statistical Review of World Energy.[2] Using one source for both series eliminates the definitional mismatches that plague cross-dataset energy accounting.

Input 1 — CO₂ intensity of energy (Mt CO₂ per EJ)

For each country and year, divide CO₂ emissions from energy combustion[3] by total primary energy supply in exajoules.[4] The result — megatonnes of CO₂ per exajoule — measures how dirty each unit of energy is, independent of how much energy the country uses or how large its economy is. It is the purest single measure of an energy system’s decarbonization, and it is deliberately expressed against primary energy, not electricity: electricity-only measures flatter countries that have cleaned their grids while leaving transport, heat, and industry untouched.

Figure 1 shows the six trajectories. Three features carry the story. France breaks from the pack in 1980 and never returns. Japan converges steadily for three decades, then reverses sharply in 2011 when it shuts its reactors — the only line in the chart that goes materially backwards.[5] And Australia enters the period as the most carbon-intensive energy system of the six and exits the same way, having improved less in 48 years than France managed in its first six.

Figure 1. CO₂ intensity of primary energy, six countries/regions, 1978–2025. Source: Energy Institute Statistical Review of World Energy.

Input 2 — Total primary energy supply (EJ per year)

The second input is each country’s actual total energy supply in exajoules per year (Figure 2). This series does the scaling: a given intensity gap matters thirty times more in the United States (~95 EJ) than in Australia (~6 EJ). In the counterfactual it is held exactly at its historical values — the analysis changes what the energy is made of, never how much of it there is.

Figure 2. Total primary energy supply, 1978–2025. Source: Energy Institute Statistical Review of World Energy.

The calculation

With the two inputs defined, the excess for country c in year t is a single line of arithmetic:

Excess(c, t) = [ Intensity(c, t) − Intensity(France, t) ] × Energy(c, t)

Annual excesses are summed from 1978 through 2025 to produce cumulative totals. One robustness note: in no country-year does any of the five economies achieve a lower intensity than France, so the excess is uniformly positive and no clipping or special-case handling is required. The gap never closes; it only varies in width.

3. The Resulting Excess CO₂

Figure 3 shows the annual CO₂ excess by country. Two patterns deserve narration. Through the 1990s and 2000s — the decades of Kyoto, of climate summitry, of the first renewables mandates — the annual excess for the United States and the European Union is flat or rising. The gap versus France only begins to close meaningfully after roughly 2007, and in the American case the driver is the shale-gas displacement of coal, not renewables policy. Japan’s excess, meanwhile, widens after 2011 even as everyone else’s narrows.

Figure 3. Annual excess CO₂ relative to the France-intensity counterfactual, 1978–2025.

Stacking the same series (Figure 4) shows the aggregate flow: the five economies together have emitted roughly 4 to 4.5 Gt of avoidable CO₂ per year, essentially without interruption, for four decades. Even in 2025 the flow is still running at about 4.2 Gt per year — more than a tenth of global fossil CO₂ emissions, from the intensity gap alone.

Figure 4. Annual excess CO₂, stacked, 1978–2025.

Cumulating the flows produces the headline result (Figure 5). By 2025 the five economies have emitted 184.9 Gt of CO₂ beyond what France’s demonstrated trajectory required. For scale, the central estimate of the world’s entire remaining carbon budget for a 50% chance of holding warming to 1.5°C is about 130 Gt CO₂.[6] The avoidable emissions of five economies — not the world; five economies — exceed the whole planet’s remaining 1.5°C allowance by roughly 40%. The cumulative total crossed the 130 Gt line around 2012.

Figure 5. Cumulative excess CO₂ versus the France-intensity counterfactual, with the remaining 1.5°C carbon budget for reference.

Table 1 and Figure 6 give the per-country decomposition. The United States accounts for half the total on the strength of its energy scale; the European Union contributes 56.5 Gt despite a respectable intensity trajectory, again because of scale; Japan’s 20.3 Gt is disproportionately a post-2011 story.

Table 1. Cumulative and current-year excess CO₂ by country.

Figure 6. Total avoidable CO₂, 1978–2025, by country.

4. Reading the result correctly

Three caveats keep the number honest. The counterfactual holds energy consumption fixed, so it ignores any rebound or price effects a real nuclear build-out might have produced — effects that could push the number in either direction. It uses combustion CO₂ only, excluding methane and process emissions, which makes 184.9 Gt a floor rather than a ceiling for the full greenhouse-gas gap.[7] And it asks nothing of the five economies that France did not ask of itself: the benchmark includes France’s own maintenance crises, its post-Messmer construction slowdown, and its recent reactor outages.

What the number establishes is narrow and, for that reason, durable: with technology available in 1978, at a pace demonstrated by a real economy under real political constraints, five Western-aligned economies could have kept an amount of CO₂ out of the atmosphere larger than the entire carbon budget the world now has left. The constraint was never technical.

5. The Number in Context

Large numbers fail in isolation. 184.9 Gt of carbon dioxide is beyond intuition — nobody has ever seen a gigatonne. What follows are five comparisons, each computed from the same Energy Institute dataset that produced the headline result, that translate the counterfactual into scales a reader can hold [6].

• It is 9.5 times more CO₂ than every wind turbine and solar panel on Earth has avoided in all of history. Cumulative global wind and solar generation from 1978 through 2025 — now running at 5,525 TWh per year — has avoided roughly 19.5 Gt of CO₂. The five economies’ intensity gap versus France is nearly ten times that. Five decades of the technology most often presented as the answer has not yet offset one decade of the question.

• It exceeds the combined emissions of two continents. The entire African continent and all of South & Central America together emitted 88.8 Gt of CO₂ from energy over the same 48 years. The avoidable emissions of five wealthy economies are more than double the actual emissions of roughly two billion people.

• It equals three Indias. India — 1.4 billion people, industrializing across the entire period — emitted 60.9 Gt from 1978 through 2025. The counterfactual is three times that.

• It is more than five years of the entire world. At 2025’s global rate of 35.8 Gt per year, 184.9 Gt is equivalent to switching off every power plant, vehicle, ship, furnace, and factory on the planet for more than five years.

• It is China, erased for sixteen and a half years. At its current rate of 11.2 Gt per year, the counterfactual equals shutting down the world’s largest emitter entirely for 16.5 years — or, framed domestically, 39 years of total United States emissions at today’s rate.

The comparisons compound the paper's conclusion rather than merely decorating it. The gap was not marginal, and it was not close. It was larger than continents, larger than the remaining budget, and larger than the entire lifetime contribution of the technologies that displaced nuclear power in the West's political imagination. The constraint was never technical. What the constraint actually was — a fifty-year campaign of organized opposition that made the safest, cleanest large-scale energy source synonymous with danger in the public mind — is documented in a companion essay [8]. This paper's contribution is narrower: to put a number on what that campaign cost the world. That number is at least 184.9 gigatonnes.

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[1]France’s 1974 Messmer plan launched the construction of what became 56 pressurized-water reactors over roughly 15 years, displacing oil- and coal-fired generation. Nearly all of France’s intensity separation from its peers occurred during this single deployment decade.

[2]Energy Institute, Statistical Review of World Energy 2026 (data through 2025), consolidated dataset (EI-Stats-Review-ALL-data.xlsx), sheets “CO2 from Energy” and “Total Energy Supply (TES) -EJ.” Available at

https://www.energyinst.org/statistical-review

[3]“CO2 from Energy” covers carbon dioxide from the combustion of fossil fuels for energy. It excludes methane, natural-gas flaring, and industrial process emissions (e.g., cement calcination), which the Statistical Review reports separately. Using the narrower combustion series makes the counterfactual conservative.

[4]The Statistical Review reports total energy supply on an input-equivalent (substitution) basis: electricity from nuclear, hydro, and other non-fossil sources is converted to the primary energy that a thermal plant would have consumed to generate it. Because the same convention is applied to every country and every year, it does not bias the cross-country intensity comparison that drives this analysis.

[5]Japan’s intensity had tracked the Western pack until the post-Fukushima nuclear shutdowns of 2011–2012, after which it rose roughly 10 Mt CO₂/EJ and, as of 2025, has not returned to its 2010 level.

[6]Forster, P. M., et al. (2025), “Indicators of Global Climate Change 2024,” Earth System Science Data 17, 2641–2680: central estimate of the remaining carbon budget for a 50% chance of holding warming to 1.5°C is 130 Gt CO₂ from the beginning of 2025.

[7] These comparisons share a discipline: every figure is drawn from the Statistical Review’s “CO2 from Energy” series over the identical 1978–2025 window, so no definitional sleight of hand connects them. The wind and solar figure converts cumulative generation to input-equivalent primary energy at 40% thermal efficiency, valued at each year’s world-average CO₂ intensity; an independent cross-check using a standard displaced-generation factor of 0.55 t CO₂/MWh yields the same 19.5 Gt. The regional and national comparisons are straight cumulative sums; the annualized comparisons use 2025 single-year values.

[8] Scott Grout, "The Verdict on Nuclear Energy: Who Killed the Future?" Needs of the Many, May 11, 2026. https://needsofthemany98.substack.com/p/the-verdict-on-nuclear-energy-who

https://essd.copernicus.org/articles/17/2641/2025/

The 2026 update of the same series again reports a 130 Gt CO₂ remaining budget, restated from the beginning of 2026. The Global Carbon Project’s 2025 budget uses a different framework and reports a higher figure (~170 Gt); the conclusion here does not depend on which estimate is used.