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change in global CO₂ emissions
CarbonBrief and OurWorldInData have produced some excellent articles showing how countries contribute to global warming over time.
However, when I looked at the data – thanks to OWID for sharing it – I realized that they accumulate, year after year, the CO2 emitted by each country. However, as the IPCC points out in its report, a significant proportion of the carbon emitted (44%) has been absorbed and no longer contributes in the strict sense to global warming.
However, CarbonBrief, like OWID, justifies accumulating all the carbon emitted, as this would contribute for decades. In support of this position, Carbon Brief highlights a study that :
- In their view, this underlines a flaw in a previous study which indicated that the peak contribution of emitted CO2 was around ten years away.
- They highlight the impact of the level of carbon emitted by studying several emissions scenarios, as if the carbon were emitted all at once, and at levels 100x to 500x higher than global annual emissions.
- They defend the interest of their study by explaining that “These cumulative emissions result from a succession of small emission pulses, and the response time for the total emission is the average response time for these individual pulses.”… certainly, but as much as the 100GtC will indeed probably be reached according to this accounting, the interest of simulating 1000GtC or 5000GtC seems questionable.
- Above all, they themselves point out that “this means that warming due to past CO2 emissions is small and that future warming will be largely determined by current and future CO2 emissions.“
So self-flagellation aside, the logic of counting all emissions seems questionable, to say the least.
So I recalculated the total carbon emitted over time, but with an absorption factor. Based on the fact that in 100 years, around 60% of excess carbon has been absorbed by the ocean, and the same by biomass, I’ve assumed an absorption factor of 1.5% / year.
the following graph shows the evolution of carbon (fossil + forest and land use) over time – because it looks pretty, knowing that the main thing is the impact of these emissions today.
Cumulated carbon emission as of today impact ( millions tonnes of CO2 )
OWID version - fully cumulated carbon - ( millions tonnes of CO2 )
Carbon intensity index by country
Par ailleurs, dans leur recherche de responsables, ces sites réalisent des analyses par pays et également par habitant, blâmant tantôt l’individu ( per capita emissions) , tantôt le pays. Notamment Carbon Brief réalise 2 calculs qui “aborde la question de la prise en compte des tailles de population relatives… Ces approches donnent des résultats sensiblement différents, soulignant le défi que représente l’interprétation des émissions cumulées par habitant”. Outre le fait que les 2 méthodes utilisées tiennent à nouveau compte du total non “amorti” des émissions, elles ont le biais implicite d’ignorer l’éléphant dans la pièce, la taille de la population, vu comme une variable totalement naturelle et positive, donnant du coup effectivement une prime à qui est le plus gros ou, plus exactement, puisque leur base est toujours l’émission par pays, qui est le plus gros par surface disponible. Car puisque l’on parle de ressources, d’une seule Terre, je suis surpris que jamais la question de la densité de la population n’intervienne dans le débat : n’est-ce pas de la responsabilité de chaque nation de faire une utilisation raisonnée des ressources, donc in fine de la surface disponible ? Quand l’Inde est quatre fois plus dense que la France et émet 10x plus de CO2 (en 2022) pour 6x la surface, est-ce vraiment la France le mauvais larron ?
Je propose donc d’ajouter un autre indicateur, les émissions par surface disponible c’est-à-dire un indice d’intensité carbone, qui compare les pays entre eux indépendamment de la population, parce que si chaque individu est responsable, les discussions et les compensations interviennent au niveau des États.
Credit: made with observableHQ
NB: a large number of countries have much higher indices (Singapore, Bahrain, Belgium, the Netherlands, many islands, etc.), but here we limit ourselves to the list of countries shown above.
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