What are carbon budgets and carbon footprints?

Climate change is everywhere. Even amidst the coronavirus crisis, many articles remind us that climate disruption will take over this bad news cycle. This is proof that the issue remains a major concern.

It mobilizes world leaders and international organizations, who have made a habit of gathering annually in different cities for the Conferences of the Parties (COPs). The 26th edition of these conferences will take place in 2021 in Glasgow.

COPs follow one another, but with what success?

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Our goal

So what exactly is our goal? We must reduce our greenhouse gas emissions: carbon dioxide (CO2), the most talked-about, but also methane (CH4), nitrous oxide (N₂O), etc.

To make things easier, a complex calculation allows all these gases to be expressed as CO2 equivalent (CO2e), one single measure to rule them all.

That little "e" in CO2e is far from trivial: a Paris-New York round-trip flight emits 1 ton of CO2, but 2 tons of CO2e!

📗 Read this glossary for more details.

Why are these gases so concerning? The more we emit, the more they accumulate in the atmosphere and heat the Earth. Today, the planet's average temperature has already increased by more than 1.2°C since the early 1900s.

After reviewing countless grim scientific studies on the consequences of global warming, world leaders made a decision in late 2015 : the Paris Agreement:
we must do everything that is possible **to limit global warming well below 2°C and strive to keep it under 1.5°C. **

We are heading for disaster

Clearly, we have not taken that direction. The United Nations assessed global commitments, revealing that **our current trajectory leads to 3.2°C of global warming **and that’s assuming every country meets its promises.

Is that really catastrophic? Yes.

We know this thanks to the IPCC, a massive international scientific effort summarizing a growing alount of climate research.
We are all familiar with the consequences: rising sea levels, more frequent and intense heatwaves, droughts, hurricanes... Thus, leading to famines, mass migrations, and species extinctions.

But grasping the scale of these changes remains difficult. Let’s take a quick look at heatwave projections for France following the worst-case scenario.

Illustration from a JDD article and a French study using scenario RCP8.5.

This map is already alarming, but even more so when comparing heatwave-related deaths to those caused by the coronavirus pandemic.

Red: COVID-19; Yellow: 2003 heatwave. Source: INSEE

The speed of human-induced warming is unprecedented:
We are changing the climate within a century, whereas past "natural" warming events unfolded over thousands of years, giving ecosystems time to adapt.

For a visual representation, check out this timeline.

Why is action so difficult?

To limit global warming, we must reduce CO2 emissions. The same applies to other greenhouse gases, but for now, we will focus on CO2.

What is our limit?

Calculating this is complex : scientists model oceans, land, and clouds, like an ultra-realistic video game. But fortunately, they have created a clear and simple summary.

Warming Level	Our budget (Jan 1, 2018)	Our budget (Jan 1, 2020)
1.5°C	420 billion tons of CO₂	336 billion tons
1.75°C	800 billion tons	716 billion tons
2°C	1,170 billion tons	1,086 billion tons

Source: Table 2.2 from the IPCC SR1.5 report

So, to have a two-thirds chance of staying below 1.75°C, we must not emit more than 716 billion tons of CO2 from January 1, 2020, onward.

You might wonder: does the planet "replenish" our budget over time? Yes it does. The Earth absorbs some CO2 naturally through carbon sinks. Therefore, our goal is to return to equilibrium, emitting only what the planet can absorb.

This is what we call carbon neutrality and we are currently far from achieving it.

📗 To learn more about CO2 sinks, read this article or this official report.

What about France?

Very well, the world has a simple target to meet: 716 billion tons. Simple, but not very perceptible: how many Eiffel Towers does it represent?

To make it real, these billions need to be assigned to each country. What is France’s contribution? There are countless ways to solve this diplomatic question. Should long-time industrialized countries that have already used their share step aside for others? Or should we be more lenient with these nations, allowing them to ease their transition.?

The most unbiased option might be to assign each human an equal budget, starting the countdown on January 1st, 2016, the day after the famous Paris Agreement, as suggested by this article.

For example, Canada has about half the population of France, so its national budget is half of ours. Yet, Canada emits three times more CO2 per capita than we do! They have been depleting their budget at an alarming rate since 2018, and their effort will have to be massive.

Who accounts for my smartphone’s emissions?

One important factor complicates these calculations. France has deindustrialized: the Minitel was built in Alsace, but the latest smartphone is made in Asia.

If we consider that the citizen purchasing an HD television is responsible for all the pollution associated with its production, then we are talking about their carbon footprint.

The same goes for oil: if the gasoline used by car is accounted for in France’s emissions, we must not forget that this oil was extracted for my use, for example, in Saudi Arabia.

Below, we can see that emissions from China, the world's factory, are redistributed when we take a consumption-based approach. In France, our national CO2 emissions are decreasing… but our carbon footprint has remained stable since 1990 (despite already planning to reduce it)!

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What about me?

Now, let’s set aside national approaches and outsourcing complexities to look at anndividual scale. As mentioned earlier, we need to limit future emissions to ~700 billion tons of CO2. Conveniently, there are about 7 billion people on Earth. This means my personal carbon budget is 100 tons of CO2 to stay below 1.75°C. Is that a lot? According to the Ministry of the Environment, an average French citizen emitted 8 tons of CO2 in 2018.
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Remember: the IPCC’s carbon budgets are given in CO2 only, so we are not counting the 3.2 tons of methane and other greenhouse gases emitted.

With a budget of 100 tons, if I emit 8 tons per year, I will reach my limit in 2032.
So, do we have 12 years before taking action?

Of course not! As shown in the graph above, aiming for carbon neutrality in 2032 without action until then is unrealistic, the drop would be too severe. To descend a mountain, you take switchbacks to reduce the slope.

Likewise rather than talking about a 2 tons-target or even a 1-ton target by 2050, we must map out a year-by-year trajectory that respects the carbon budget.

Here, we have doubled the timeframe, but we have cut the total CO2 in half, staying within the 100-ton budget.

A quick calculation shows the scale of the effort required each year until 2045:
-4% of our current footprint per year, which means 320 kg less CO₂ emissions each year than the previous year. If we do nothing for 5 years (as we have done so far), the required effort will be even greater and likely quite impossible in the following years.

Designing reduction scenarios

Is a 320 kg annual reduction significant? Everyone may judge this effort differently, but it’s helpful to illustrate it with actual lifestyle changes. Here’s an example scenario that aligns with this yearly reduction:

• starting in 2020, I drive 2,000 km less per year (or carpool 20 km per day).
• in 2021, I give up my annual flight to Croatia (but not my holiday: I take the night train via Paris-Venice instead).
• in 2022, I permanently remove two beef steaks per week from my shopping list, if that was still the case.
• starting in 2023, I lower my home’s temperature by 1°C (and buy a high-quality wool sweater that will last 10 years). - in 2024, I cut my alcohol consumption by a third, or limit myself to locally brewed draft beers.
• in 2025, I do not replace my laptop (I can buy a second-hand one and keep it for 5+ years).
• …

Of course, these are just examples, there are many other ways to achieve the goal, and without a strict or set program.

Limiting risk vs. achieving balance

We just explored a scenario to limit warming to 1.75°C. However, we each have the option to do far better than these carbon budgets, which only minimize climate damage. By transitioning to a sustainable lifestyle under 2 tons of CO2 per person, we can align with our country’s natural ability to absorb emissions. Every tenth of a degree matters.

We are 7.5 billion passengers on this ship

But we are not the only actors at stake. This individual approach helps us grasp the scale of the effort required, but it must go hand in hand with broader efforts, which have been insufficient so far:

• companies (for example, by 2025, a laptop could emit only 100 kg of CO2 and should last much longer).
• the State through its own emissions (public services, which cannot be reduced individually, account for 1.5 tons of CO2 per person per year) or through laws regulating production and consumption.
• other countries, if half of the world’s nations refuse to act, the efforts of the rest will not be in vain but will not be enough.

Individual and collective action are inseparably linked, and both are necessary.

Let's start working on reducing those first 320 tons of carbon emissions. Are you ready?

Calculate your carbonfootprint!