Who has contributed most to global CO2 emissions?

Since 1751 the world has emitted over 1.5 trillion tonnes of CO2.1 To reach our climate goal of limiting average temperature rise to 2°C, the world needs to urgently reduce emissions. One common argument is that those countries which have added most to the CO2 in our atmosphere – contributing most to the problem today – should take on the greatest responsibility in tackling it.

We can compare each country’s total contribution to global emissions by looking at cumulative CO2. We can calculate cumulative emissions by adding up each country’s annual CO2 emissions over time. We did this calculation for each country and region over the period from 1751 through to 2017.2

The distribution of cumulative emissions around the world is shown in the treemap. Treemaps are used to compare entities (such as countries or regions) in relation to others, and relative to the total. Here countries are presented as rectangles and colored by region. The size of each rectangle corresponds to the sum of CO2 emissions from a country between 1751 and 2017. Combined, all rectangles represent the global total.

There are some key points we can learn from this perspective:

• the United States has emitted more CO2 than any other country to date: at around 400 billion tonnes since 1751, it is responsible for 25% of historical emissions;
• this is twice more than China – the world’s second-largest national contributor;
• the 28 countries of the European Union (EU-28) – which are grouped together here as they typically negotiate and set targets on a collaborative basis – is also a large historical contributor at 22%;
• many of the large annual emitters today – such as India and Brazil – are not large contributors in a historical context;
• Africa’s regional contribution – relative to its population size – has been very small. This is the result of very low per capita emissions – both historically and currently.

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