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Carbon budgets

Alasdair Skelton, Professor at Stockholm University explains the basics of fair sharing of the remaining carbon budget.

The remaining carbon budget is calculated globally from the amount of carbon which can still be added to the air with a reasonable chance that global warming will not exceed some given temperature threshold.

This is “well below 2°C above pre-industrial levels” according to the Paris Agreement, which also states that we will “pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels”.

Fair sharing of the remaining carbon budget

There are different views on how the remaining carbon budget should be distributed between countries (Raupach et al., 2014). These range from “equality”, whereby the distribution between countries is based on an even distribution per capita, to “inertia” (sometimes called “grandfathering”), whereby the distribution between countries is based on a continuation of the current distribution of emissions, which means that historically larger emitters receive a larger share of the remaining budget. 

In addition to “equality”, Höhne et al. (2013) proposed “responsibility” and “capacity” as additional principles of equality. “Responsibility” refers to the historical contribution to global emissions. “Capacity” applies to both “ability to pay” and the principle of “basic needs” (or “right to development”) – meaning that a less “capable” country should be allowed “a less ambitious reduction effort to secure its basic needs”.

Höhne et al. (2013) argue that “both principles have their origins in Article 3 of the UNFCCC which states that countries should act on the basis of ‘common but differentiated responsibility and respective capabilities’, CBDR&RC)”. 

Counting emissions

Greenhouse gas emissions can be counted in different ways. Territorial emissions are emissions within a country’s borders. Productions-based emissions also includes a so-called “residential adjustment” (which can be positive or negative) so as to encompass emissions from a country’s production both inside and outside of its borders. Consumption-based emissions are emissions from consumption within a country. These emissions can occur inside and outside of its borders. 

As a “rule of thumb”, high-income countries tend to have higher consumption-based emissions, whereas low-income countries are more likely to have higher territorial emissions.

It is also worth noting that sometimes, countries count carbon dioxide emissions (referred to as CO2 emissions) whereas at other times, countries count greenhouse emissions (referred to as CO2e emissions). In the latter case, other greenhouse gases are weighted according to their global warming potential. For example, methane emissions are multiplied by a factor (27-30) because, averaged over 100 years, one molecule of methane will warm the Earth by a factor of 27-30 times more than one molecule of carbon dioxide.

Finally, when calculating emissions of a product or service, we need to consider emissions at all stages of the lifetime of that product or service. In other words, we perform a Life Cycle Assessment. We will explore this further in the next step.

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Climate and Energy: An Interdisciplinary Perspective

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