Protecting the planet and the ecological transition

A global problem of the atmosphere has already been solved once. We know why, because we measured it.

This page tells how. It also tells why this does not carry over directly to the problem of the climate.

Protecting, and changing the system

Two very different approaches hide behind the word “ecology”, and confusing them prevents us from understanding what works.

To protect is to shelter. A protected area is marked out — national park, reserve, marine zone — where certain activities are banned or regulated. Threatened species are listed and placed off limits. Damaged environments are restored: replanting a forest, reopening the course of a river, reintroducing a species that has disappeared locally.

This approach has measurable results. It also has a structural limit: the whole planet cannot be turned into a reserve, and a protected area offers no protection against anything that comes from the atmosphere or the ocean — neither warming, nor acidification, nor pollutants carried by the wind.

The transition means changing the way we produce and consume, everywhere and not only in the reserved areas. It works through four levers.

• Energy. Replacing coal, oil and gas — whose combustion releases the carbon dioxide accumulated underground over millions of years — with sources that emit little or none of it: solar, wind, hydropower, nuclear, geothermal. These sources are called renewable when they replenish themselves on a human timescale.
• Materials. Making things with less, repairing, reusing, recycling — rather than extracting, using once, throwing away.
• Land. Feeding eight billion people while clearing less land and degrading soils less.
• Demand itself. Consuming less energy and material, which is called sufficiency. It is the most debated lever, because the other three are technical and this one is not.

None of these levers is enough on its own, and they cannot substitute for one another. An electric car settles the question of fuel, but not that of the metals that must be extracted for its battery, nor that of the space it takes up.

The difference in scale between the two approaches is essential, because it is the subject of this page. Protecting the ozone layer required replacing a handful of gases, made by a small number of companies and used in a few industries. The climate transition requires transforming the entire global energy system, after two centuries of development built on fossil fuels.

And there is a difference in cost, not only in scale. For the ozone layer, known replacement products could do the same job as the banned gases, and the decision could be taken at limited cost. For the climate, the political calculations are far more complicated and the sums at stake far higher.¹¹

The first problem has been solved; that is no reason to believe that the second will be solved in the same way.

The recovery, with its dates

Our page on the atmosphere (7.7) describes in detail the discovery of the hole in the ozone layer in 1985 and the signing of the Montreal Protocol in 1987.

Observations now make it possible to establish the following.

The 2022 scientific assessment carried out by the WMO and UNEP indicates that, if current policies are maintained, ozone will return to its 1980 values:

• Around 2040 for the near-global average;
• Around 2045 above the Arctic;
• Around 2066 above the Antarctic.²²

In addition, the total amount of chlorine in the lower atmosphere was, in 2020, about 12% lower than its 1993 peak.³³

These dates come from a report published every four years. We cite the 2022 edition; the next is announced for the end of 2026. Whenever you see the phrase “the most recent assessment”, always check what year it dates from — this is true here as everywhere else on this site.⁴⁴

The caveat, stated in the report itself

One feature makes this scientific assessment sound and directly citable.

Outside the Antarctic region, the authors themselves describe the evidence of recovery as limited and held with a low level of confidence.⁵⁵

They do not merely announce an overall result. They state, point by point, the degree of certainty that can be attached to it — and they explicitly flag where the data remain fragile.

A piece of scientific work that sets out its own limits is more reliable, not less.

What did not work — and how we found out

After 2012, the decline of one of these banned gases — CFC-11 — slowed for no known reason.⁶⁶

No state had reported any renewed increase in its production.⁷⁷

It was direct measurement of the air that revealed the anomaly. At observation stations spread across the globe, the composition of the atmosphere is recorded continuously. The data no longer matched the official declarations: the air contained more of the gas than legal production could account for.

How a clandestine source is tracked down from an island

The approach is remarkable, and it comes down to three steps.

One. Very frequent measurements are available from two stations: one at Gosan, in South Korea, the other at Hateruma, in Japan.⁸⁸

Two. When the wind comes from a certain direction, the concentration rises. By cross-referencing these peaks with models of air circulation — which calculate where the air mass arriving at the station came from — the region of origin is traced back.⁹⁹

Three. The calculation points to eastern mainland China, and more precisely the area around two northeastern provinces. Emissions there exceed those of the previous period by about seven thousand tonnes a year.¹⁰¹⁰

This excess represents at least 40 to 60% of the global rise.¹¹¹¹

There remains a step that most accounts leave out: the authors also looked elsewhere. They found no significant increase in the other countries of East Asia or in any other region of the world where the data made it possible to detect one.¹²¹²

Finding a cause is not enough. One must check that there are no others. Rumford had done the same with his cannon shavings two centuries earlier.

The 2022 assessment estimates that this unreported production, from 2012 to 2019, delays the return of polar ozone to its 1980 level by at most three years.¹³¹³

The impact of the controls

From 2018 to 2019, global emissions of this gas fell by about a quarter: 26%, give or take 9 points. In eastern China, they fell by about ten thousand tonnes a year compared with 2014-2017, returning in 2019 to their pre-2013 level.¹⁴¹⁴

In 2019, global emissions returned to a level close to their 2008-2012 average.¹⁵¹⁵

Announced vs implemented: two notions to distinguish

To assess public policies for the ecological transition, a simple interpretive framework is called for.

A measure that has been announced is not a measure that has been implemented.

Between the political decision and the result on the ground come several key steps: drafting the texts, passing the law, publishing the implementing decrees, allocating the budget, setting up inspections, and implementation deadlines. Each of these steps can alter the scope of a measure, delay it or render it ineffective.

Why this distinction is essential

Target data and outcome data are often described in the same words.

When a publication mentions that a state “has decided to reduce its emissions by X%”, one should check whether this is a political target or a reduction actually measured.

• A target is decreed.
• A reduction is measured.

The three checking questions

Faced with any claim about the ecological transition, three methodological checks are enough:

1. Is it a target or an observation? Any future deadline denotes a target.
2. What is the reference year? A 30% reduction calculated relative to 1990 does not represent the same effort as a 30% fall calculated relative to 2015. A percentage means something only in relation to its starting point.
3. What is the scope being counted? Are these territorial emissions (produced on national soil) or the carbon footprint (including emissions linked to imported products)? Both indicators are valid, but they can move in opposite directions for the same country.

Why the ozone model does not carry over to the climate

It would be inaccurate to conclude that the management of climate change will follow the same trajectory as that of ozone-depleting gases.

Three structural characteristics fundamentally set these two issues apart:

Sources for the table¹⁶¹⁶

These differences do not indicate a technical impossibility, but they confirm that the two problems do not involve the same scales or the same levers of action.