Here are a few things to help you understand it, answer the question and understand your own carbon footprint.

1. Before the footprint, let's talk carbon

Carbon is a molecule that occurs naturally on our planet and is essential to life on earth. Its chemical formula is C. It is present in plants, in the soil and in the atmosphere in the form of carbon dioxide: CO2 (one carbon atom + two oxygen atoms = carbon in the form of a gas)... in short, it's everywhere! It's partly thanks to carbon that we live on a habitable planet, that we can breathe and feed ourselves.

A. So what's the problem?

The problem is that while the amount of carbon on Earth is stable, the distribution of this carbon between the atmosphere, the soil, plants and the rest of living organisms has been changing radically over the last few decades.

In particular, the amount of carbon in the atmosphere has increased sharply, and this is having an impact on the climate. The carbon in the atmosphere traps the sun's rays in the earth's crust: this is known as the greenhouse effect. In other words, it's getting hotter. And it's going to get worse for decades to come.

concentration of carbon in the atmosphere, in parts per million (ppm): data from ice cores before 1958, Mauna Loa measurements since](/images/misc/ges-evolution.png)

Carbon concentration in the atmosphere, in parts per million (ppm): data from ice cores prior to 1958, Mauna Loa measurements since then.

B. Why is this heat a problem?

It is problematic in many ways. The planet has never warmed up so quickly in the history of life. This extra heat is far from being evenly distributed over the Earth's surface, and is generating very sudden changes in climate here and there, with the consequences that go with them: melting ice and rising sea levels, an increase in fires, and so on

In terms of climate, ocean currents are being altered, leading to more numerous and more violent storms.

the nine planetary limits, image from notre-environnement.gouv.fr](/images/misc/9-limites.png)

The nine planetary limits, image from notre-environnement.gouv.fr

Climate change is only oneof the nine planetary limits, but it is probably the most important, because it has direct consequences on most of the other limits. Biodiversity, for example, has no time to adapt or migrate, and is gradually disappearing.

C. How does carbon get into the atmosphere?

Carbon is "released" into the atmosphere by our human activities, which extract it from plants and soil and burn it. In this process, carbon C is transformed into carbon dioxide CO2, which is then released into the air. This is the case for wood felled for heating, for example. But the worst source of carbon emissions into the atmosphere is the use of oil as a fuel.

Oil is made up of ancient plants that have been sedimented and gradually buried in the ground over millions of years. The carbon concentration of oil is very high. Burning it to run an engine releases a large quantity of CO2 into the atmosphere, carbon that took millions of years to store in the ground.

2. Other gases

No, it's not just carbon that poses a problem. Other gases are also responsible for climate change. Like carbon, releasing them into the atmosphere increases the absorption of solar radiation, and therefore global warming. These are known as greenhouse gases. Like carbon, they occur naturally on Earth, but humans are releasing more and more of them into the atmosphere as a result of their activities.

A. The seven types of greenhouse gas

We're just going to list them here, because it would take far too long to go into all their specifics, and that's not the point here. In addition to carbon dioxide, there are :

• Methane
• Nitrous oxide
• Hydrofluorocarbons
• Perfluorocarbons
• Sulphur hexafluoride
• Nitrogen trifluoride

  B. The concept of CO2 equivalent, or CO2e

To measure the contribution of all these gases to the greenhouse effect, we compare their "global warming potential" (GWP), i.e. their capacity to retain solar radiation in the atmosphere, with that of carbon dioxide. Emitting one tonne of methane into the atmosphere, for example, is equivalent to emitting 28 tonnes of CO2. Methane is said to have a GWP of 28.

When we talk about global warming, or greenhouse gas emissions, we use the notion of CO2 equivalent, often written CO2e, or CO2eq, which enables all greenhouse gases to be included in the calculations.

source

](/images/misc/ges-monde.png)

Source

3. Back to the broadcasts

As we said at the beginning, our activities have been releasing more greenhouse gases (CO2e) into the atmosphere for several decades than the natural carbon cycle or other greenhouse gases. As individuals, each and every one of us contributes to this greenhouse effect through our activities, which could be described as "modern":

• Consumption of oil to run machinery (often vehicles)
• Consumption of electricity to run our equipment
• Soil artificialisation (preventing the soil from gradually 'capturing' CO2 from the atmosphere): buildings, transport infrastructure, intensive agriculture, etc
• Industrial farming practices and the preponderance of meat-based foods
• Consumption of oil and other materials to put an ever-increasing quantity of manufactured products into circulation

Calculating our contribution to climate change means calculating the extent to which our uses contribute to the release of CO2 equivalents into the atmosphere.

A. The reduction target

On average, the French emit 9.2 tonnes of CO2e per year (figure from the Service des Données et Études Statistiques for 2022, Ministry for Ecological Transition). This average varies widely depending on lifestyle, whether or not they use a car or aeroplane, whether they live in a house or flat, their heating system, their diet, etc. Most people emit between 4 and 15 tonnes per person per year. That's far too much for the planet to absorb. Experts agree that to maintain a livable Earth for all, we need to reduce this footprint to 2 tonnes of CO2e per person per year.

breakdown of footprints calculated on the Nos Gestes Climat website - OpinionWay survey](/images/misc/empreinte-france.png)

Breakdown of footprints calculated on the Nos Gestes Climat website - OpinionWay survey

Quite a target, and one that calls for us all to roll up our sleeves!

B. Let's get calculating

The aim of the carbon footprint simulator is to find out where you stand in relation to the overall target of 2 tonnes of CO2 equivalent, and to understand what your main greenhouse gas emissions are, and how you could reduce them. What everyday actions emit the most? Are there alternatives that emit less, or none at all?

To do this, we're asking you to describe some aspects of your lifestyle: transport, food, housing and consumption.

In 2020, ADEME (the French Environment and Energy Management Agency) launched Nos Gestes Climat, a completely open, free and well-documented online calculator for calculating your individual footprint. Educational, it invites you to carry out your individual carbon footprint in just a few minutes. Contributory, it allows users to question, suggest or criticise the simulator, thereby contributing to its quality.

Isn't it time to know your carbon footprint?