Flying is one of the most carbon-intensive activities, yet it contributes just 2.5% of the world’s carbon emissions
Increased demand and technological improvements have driven the change in aviation emissions over the last 50 years.
Total CO2 emissions are often explained through the “Kaya identity” — how many people there are, their income, the energy efficiency of economies, and the carbon intensity of energy.
We can use a similar framework to understand the drivers of aviation emissions.
The Kaya identity is a mathematical identity stating that the total emission level of the greenhouse gas carbon dioxide can be expressed as the product of four factors: human population, GDP per capita, energy intensity (per unit of GDP), and carbon intensity (emissions per unit of energy consumed).
It is a concrete form of the more general I = PAT equation relating factors that determine the level of human impact on climate.
I = P × A × T
The expression equates human impact on the environment to a function of three factors: population (P), affluence (A) and technology (T)
Although the terms in the Kaya identity would in theory cancel out, it is useful in practice to calculate emissions in terms of more readily available data, namely population, GDP per capita, energy per unit GDP, and emissions per unit energy.
It furthermore highlights the elements of the global economy on which one could act to reduce emissions, notably the energy intensity per unit GDP and the emissions per unit energy.
Where:
F is global CO2 emissions from human sources
P is global population
G is world GDP
E is global energy consumption
And:
G/P is the GDP per capita
E/G is the energy intensity of the GDP
F/E is the emission intensity of energy
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