How to Compare Carbon Emissions Across Countries: An Assessment of Different Measures and Indicators

Introduction

Carbon dioxide (CO2) is the main greenhouse gas that causes global warming and climate change. It comes from various human activities, such as burning fossil fuels, cutting down trees, farming, and making things. The amount of CO2 that a country releases can affect the environment, the economy, and the society, both in that country and in other countries. Therefore, it is important to measure and compare the carbon emissions across countries, to know the sources, reasons, and effects of the emissions, and to plan and do things to reduce them.

However, measuring and comparing carbon emissions across countries is not easy. There are different ways to calculate and show the emissions, each with its own benefits and drawbacks. Depending on the choice of the way, the ranking and result of the countries can change a lot, and so can the way we see and understand the emissions. In this article, we will look at some of the most common and popular ways of measuring and comparing carbon emissions, and talk about their good and bad points, as well as their meaning for the fairness and accuracy of the comparison.

The Top Three Emitters: China, US, and India

Before we look at the different ways of measuring and comparing carbon emissions, let us first see the top three emitters in the world: China, the US, and India.

According to the Global Carbon Atlas, these three countries together accounted for 52% of the world’s CO₂ in 2021. These three countries also have the biggest populations, the biggest economies, and the biggest energy needs in the world, all of which are the key drivers of their emissions.

However, these three countries also have different features, situations, and problems that affect their emissions and their actions to deal with them. For example, China is still a developing country, with a big and growing population (1.4 billion), a fast and varied economy, and a lot of coal use. The US is a developed country, with relatively a smaller and stable population (0.3 billion), a mature and service-based economy, and a lot of consumption. India is also a developing country, with a big and growing population (1.4 billion), a slower and rising economy, and a low income per person. These differences can matter a lot for the choice and understanding of the ways of measuring and comparing carbon emissions, as we will see in the next sections.

As a background to this discussion, it would be useful to mention that Kaya Identity connects 4 factors to explain carbon emissions at global or national level:

Carbon emissions = Population x GDP per capita x Energy intensity x Carbon intensity

Implication of Kaya Identity is that total emissions for a country reflects its population, as well as the economic development and growth (including industrialization, and standards of living) and the energy efficiency of production achieved by the country. It is therefore not surprising that countries with high GDP per capita generally have high emissions per capita.

1-Total Emissions

This is the simplest measure of how much CO2 a country emits in a given year. It shows the direct impact of a country’s activities on the atmosphere.

However, it does not account for the differences in population size, economic development, historical responsibility, or consumption patterns across countries. For example, China has the highest total emissions, but it also has the largest population and is still a developing country. On the other hand, the US has lower total emissions than China, but higher per capita emissions, which means it emits more CO2 per person than China. Total emissions also do not capture the emissions that are embedded in the goods and services that a country imports or exports, which can shift the responsibility from the producer to the consumer or vice versa.

Total emissions is technically called "production based emissions" as it measures how much CO2 a country emits from the production of goods and services within its territory in a given year. It reflects the carbon intensity and efficiency of the country's production system.

2-Emissions per Capita

Emissions per capita is the measure of how much CO2 each person in a country emits on average in a given year. It can reflect the lifestyle and consumption choices of the citizens, as well as the efficiency and cleanliness of the energy system. Rich, oil producing countries with relatively smaller population - eg, Qatar, Kuwait, and the UAE - as well as with relatively larger population - Saudi Arabia, Australia, the US and Canada - are often in the top 10 by this measure.

However, emissions per capita does not account for the differences in historical responsibility, economic development, or population growth across countries. For example, Canada has higher emissions per capita than India, but it also has a longer history of industrialization, a higher standard of living, and a lower population growth rate. Emissions per capita also do not capture the emissions that are embedded in the trade of goods and services, which can affect the fairness of the measure.

3-Emissions per unit of GDP

Emissions per $1 of the country's gross domestic product (GDP) is the way of measuring how much CO2 a country releases per unit of economic output in a year. It can show the carbon intensity and efficiency of the production system, as well as the structure and composition of the economy.

However, emissions per GDP unit does not for the differences in population size, consumption patterns, historical responsibility, or development stage across countries. For example, US or France has lower emissions per GDP unit than China, but it also has a smaller population, a more service-oriented economy, a lower consumption level, and a longer history of development. Emissions per GDP unit also do not capture the emissions that are embedded in the trade of goods and services, which can affect the fairness of the measure..

4-Total Accumulated Emissions since Pre-Industrial Era

This is the measure of how much CO2 a country has emitted cumulatively since the start of the industrial revolution (around 1750-1800). It can reflect the historical responsibility and contribution of a country to the current level of atmospheric CO2 and global warming.

However, it does not account for the differences in population size, economic development, current emissions, or future projections across countries. For example, the UK has higher total accumulated emissions than Brazil, but it also has a smaller population, a more developed economy, lower current emissions, and more ambitious climate targets. Similar is the case with the US when compared against India (and to some extent against China though China currently has the highest emissions). Total accumulated emissions also do not capture the emissions that are embedded in the trade of goods and services, which can affect the fairness of the measure.

5-Consumption based Emissions

This is the measure of how much CO2 a country emits from the consumption of goods and services within its territory in a given year. It can reflect the lifestyle and consumption choices of the citizens, as well as the carbon footprint and responsibility of the demand side. Consumption-based emissions measure is adjusted for goods and services traded across the world. It means that the emissions that are emitted in the production of goods and services that are imported are added to the consumption-based emissions of the importing country, and the emissions that are emitted in the production of goods and services that are exported are subtracted from the consumption-based emissions of the exporting country. This way, the consumption-based emissions reflect the carbon footprint of a country’s consumption and lifestyle choices, regardless of where the goods and services are produced.

However, it does not account for the differences in production patterns, trade flows, population size, or economic development across countries. For example, Japan has higher emissions based on consumption than Mexico, but it also has a smaller population, a more advanced economy, a lower production level, and more trade partners. Further, it can be difficult to calculate consumption based emissions, as it requires data on the emissions embedded in the trade of goods and services, which can be costly, inaccurate, or unavailable. For example, it can be hard to track the emissions along the complex and global supply chains, or to allocate the emissions to different consumers.

It can be misleading, as it can shift the responsibility from the producer to the consumer, or vice versa. For example, it can make the consumers feel guilty for their consumption choices, while ignoring the role of the producers in reducing the emissions. Or, it can make the producers feel complacent for their production efficiency, while ignoring the impact of their exports on the emissions of other countries

6-Emissions Intensity

This is the way of measuring how much CO2 a country releases per unit of energy used in a year. It can show the cleanliness and efficiency of the energy system, as well as the potential for improvement and transition. However, it does not consider the differences in energy demand, consumption patterns, population size, or economic development across countries.

7-Emissions per land area

This is the measure of how much CO2 a country releases per unit of land area in a year. It can show the density and distribution of the population, as well as the land use and management practices. However, it does not consider the differences in climate, geography, biodiversity, population size, or economic development across countries.

8-Emissions per forest area

This measures how much CO2 a country emits per unit of forest area in a year. It can show the role and value of forests as carbon sinks and sources, as well as the forest conservation and restoration efforts. However, it does not consider the differences in forest types, quality, age, management, population size, or economic development across countries.

9-Emissions per capita income

Emissions per capita income is a measure of how much CO2 a country releases per unit of income per person in a year. It can show the equity and justice of the emission distribution, as well as the trade-off and balance between development and environment. However, it does not consider the differences in income inequality, purchasing power, consumption patterns, population size, or economic development across countries.

10-Rate of increase or decrease in emissions

This measures how much a country’s emissions change over time, usually shown as a percentage or an amount. It can show the trend and direction of a country’s emission path, as well as the ambition and progress of the climate action. However, it does not account for the differences in baseline, historical responsibility, current level, future projection, population size, or economic development across countries.

Conclusion

In this article, we have looked at some of the most common and popular ways of measuring and comparing carbon emissions across countries, such as total emissions, emissions per capita, emissions per unit of GDP, total accumulated emissions since pre-industrial era, consumption based emissions, and other measures. We have discussed their pros and cons, as well as their implications for the fairness and accuracy of the comparison. We have also seen the top three emitters in the world: China, the US, and India, and how their different features, situations, and problems affect their emissions and their actions to deal with them.

Metrics - such as total emissions, emissions per capita, emissions per unit of GDP, and emissions per unit land or forest area - which measure the emissions for a year is a snapshot of the situation at one point of time and suffer from certain key shortcomings - they don't consider the differences in historical responsibility arising from emissions due to economic growth, industrialization and population growth. In contrast, total accumulated emission measure does not consider current emissions or future projections across countries as well as emissions embedded in the trade of goods and services, which can affect the fairness of the measure.

Measuring and comparing carbon emissions across countries is not easy. Each measure of carbon emissions has its own advantages and disadvantages, and none of them can capture the full picture of a country’s contribution to climate change. Therefore, it is important to use multiple measures and indicators to assess and compare the emissions across countries, and to consider the context and circumstances of each country. There is no one-size-fits-all solution to the climate crisis, and each country has different responsibilities, capabilities, and opportunities to act.