Analysis: Which countries are historically responsible for climate change?

Ahead of the pivotal climate conference, COP26, Carbon Brief has analysed data complying from various reliable sources to try to address national responsibility for historical CO2 emissions from 1850-2021. For the first time, the analysis includes CO2 emissions from land use and forestry, in addition to those from fossil fuels, which significantly alters the top 10

Historical responsibility for climate change is at the heart of debates over climate justice. History matters because the cumulative amount of carbon dioxide (CO2) emitted since the start of the industrial revolution is closely tied to the 1.2C of warming that has already occurred.

In total, humans have pumped around 2,500 bn tonnes of CO2 (GtCO2) into the atmosphere since 1850, leaving less than 500 GtCO2 of the remaining carbon budget to stay below 1.5C of warming. This means that, by the end of 2021, the world will collectively have burned through 86% of the carbon budget for a 50-50 probability of staying below 1.5C, or 89% of the budget for a two-thirds likelihood.

Carbon Brief has looked at national responsibility for historical CO2 emissions from 1850-2021, and for the first time, the analysis includes CO2 emissions from land use and forestry, in addition to those from fossil fuels, which significantly alters the top 10.

In first place on the rankings, the US has released more than 509 GtCO2 since 1850 and is responsible for the largest share of historical emissions, Carbon Brief analysis shows, with some 20% of the global total. China is a relatively distant second, with 11%, followed by Russia (7%), Brazil (5%) and Indonesia (4%). The latter pair are among the top 10 largest historical emitters, due to CO2 from their land.

Meanwhile, large post-colonial European nations, such as Germany and the UK, account for 4% and 3% of the global total, respectively, not including overseas emissions under colonial rule.

These national totals are based on territorial CO2 emissions, reflecting where the emissions take place. In addition, the analysis looks at the impact of consumption-based emissions accounting in order to reflect trade in carbon-intensive goods and services. Such accounts are only available for recent decades, even though trade will have influenced national totals throughout modern history.

The analysis then explores the figures in relation to population, where the likes of China and India fall down the rankings. Notably, per-capita rankings depend strongly on the methodology used and_unlike cumulative emissions, overall_these figures do not relate directly to warming.

I Video shows, by ranked nation, cumulative CO2 emissions from fossil fuels, land use and forestry, 1850-2021 (million tonnes). Bottom right, remaining carbon budget to limit global warming at 1.5C (50-50 chance). Animation by Tom Prater for Carbon Brief.

Why cumulative CO2 matters

There is a direct, linear relationship between the total amount of CO2 released by human activity and the level of warming at the Earth’s surface. Moreover, the timing of a tonne of CO2 being emitted has only a limited impact on the amount of warming it will ultimately cause.

This means CO2 emissions from hundreds of years ago continue to contribute to the heating of the planet _and current warming is determined by the cumulative total of CO2 emissions over time. This is the scientific basis for the carbon budget, the total amount of CO2 that can be emitted to stay below any given limit on global temperatures.

The link between cumulative emissions and warming is measured by the “transient climate response to cumulative emissions” (TCRE), estimated by the latest Intergovernmental Panel on Climate Change (IPCC) report to be 1.65C per 1,000 bn tonnes of carbon (0.45C per 1,000GtCO2).

Carbon Brief’s analysis shows that humans have emitted some 2,504 GtCO2 into the atmosphere since 1850, a figure that aligns with those presented by the IPCC and by the Global Carbon Project, an international effort to quantify carbon emissions and sinks each year.

Based on the TCRE, those cumulative CO2 emissions correspond to a warming of around 1.13C _and temperatures in 2020 reached around 1.2C above pre-industrial levels. (This article does not consider emissions of non-CO2 greenhouse gases or aerosols, which are predominantly short-lived and so do not accumulate over time in the same way as CO2. The warming impact of non-CO2 gases is roughly balanced by the cooling from aerosols.)

The chart shows how rapidly global CO2 emissions have risen over the past 70 years. It also highlights the split between CO2 emissions from fossil fuels and cement, shown in grey, compared with those from land use, land-use change and forestry (LULUCF, green).

(Chart: Annual global CO2 emissions from fossil fuels and cement (dark grey) as well as from land use, land-use change and forestry (green), 1850-2021 Credit: Carbon Brief)

At a global level, emissions from land use and forestry have remained relatively consistent over the past two centuries. They amounted to around 3 GtCO2 in 1850 and stand at roughly 6 GtCO2 today, despite huge shifts in regional patterns of deforestation over time. (A visible spike in 1997 was caused by widespread forest fires in Indonesia and other parts of Asia, subsequently described as an “unprecedented ecological disaster”.)

In contrast, fossil-fuel emissions have doubled over the past 30 years, quadrupled over the last 60 years and risen nearly twelve-fold over the past century. The 0.2 GtCO2 released in 1850 amounts to just half one per cent of the roughly 37 GtCO2 that is likely to be emitted in 2021.

Nevertheless, while the large majority of CO2 emissions today are from burning fossil fuels, human activity, such as deforestation, has made a significant contribution to the cumulative total. Land-use change and forestry added some 786 GtCO2 during 1850-2021, amounting to nearly a third of the cumulative total, with the remaining two-thirds (1,718Gt CO2) from fossil fuels and cement.

In terms of assigning national responsibility for current warming, it is therefore impossible to ignore the important contribution from CO2 emissions due to land-use change and forestry.

Taken together, cumulative emissions between 1850-2021 add up to some 86% of the carbon budget for an even chance of staying below 1.5C or 89% of the budget for a two-thirds chance. As emissions have increased, the carbon budget has been used up at an accelerating pace, with half the cumulative total since 1850 having been released over the past 40 years alone.

From the start of 2022, the remaining 1.5C budget (50% probability) would be used up within 10 years, if annual emissions remain at current levels_and the budget for a two-thirds likelihood of staying below 1.5C would last just seven years.

National responsibility for historical emissions

The question of who is responsible for using up the carbon budget is crucial in the context of climate justice debates. It speaks to the responsibility for dealing with the impact of climate change to date_ as well as who ought to do the most to prevent further warming.

However, assigning responsibility is far from straightforward. Carbon Brief’s analysis primarily looks at cumulative national-territorial emissions, since this is the way the available data is presented.

In loose terms, cumulative national allocations give “responsibility” for historical emissions to the modern-day country that occupies the territory that emitted in the past. Clearly, shifting territorial ownership and the unification and dissolution of countries complicates matters.

On this basis_and including all human sources of CO2_the animation above shows for the first time the countries most responsible for historical emissions as they accumulate during 1850-2021. Each bar, marked with a contemporary national flag, represents a country’s cumulative emissions over time and is colour-coded by region of the world, according to the map in the top-right corner. The year and the size of the remaining carbon budget for 1.5C as it gets used up over time are indicated in the bottom right corner.

The history of national CO2 emissions is also a history of development. While the changing positions in the rankings relate to a multitude of factors, some broad themes emerge. In the early decades of the timeline, global CO2 emissions were dominated by land-use change and forestry and this is reflected in the top 10 shown in the animation.

In this period, the largest emitters were primarily geographically extensive nations cutting down their temperate forests for agricultural land and for fuel, such as the US, Russia and China. In the US, for example, a wave of settlers spread across the continent from east to west, following their “manifest destiny” and clearing land for farming as they went.

At the same time, a few European countries (which had largely cleared their land for farming before 1850) start to rise the rankings because they were in the throes of coal-fuelled industrialisation, including France, Germany and_above all_the UK.

Although these countries have significantly reduced their emissions in recent decades, they remain among the most important contributors to historical warming today. The rainforest nations of Brazil and Indonesia were also being deforested in the late 19th and early 20th centuries by settlers growing rubber, tobacco and other cash crops. But deforestation began “in earnest” from around 1950, including for cattle ranching, logging, and palm-oil plantations.

The US remains in first position for its cumulative CO2 emissions throughout the time series, as its development continued first with widespread use of coal, then with the advent of the motor car. By the end of 2021, the US will have emitted more than 509 GtCO2 since 1850. At 20.3% of the global total, this is by far the largest share and is associated with some 0.2C of warming to date.

This is shown in the chart, which also breaks down each country’s cumulative total into emissions from fossil fuel use (grey) or land-use change and forestry (green).

(Chart: The 20 largest contributors to cumulative CO2 emissions 1850-2021 Credit: Carbon Brief)

In second place is China, with 11.4% of cumulative CO2 emissions to date and around 0.1C of warming. While China has had high land-related emissions throughout, its rapid, coal-fired economic boom since 2000 is the main cause of its current position. China’s CO2 output has more than tripled since 2000, overtaking the US to become the world’s largest annual emitter, responsible for around a quarter of the current yearly total.

Russia is third, with some 6.9% of global cumulative CO2 emissions, followed by Brazil (4.5%) and Indonesia (4.1%). Notably, the chart shows how the latter pair are in the top 10 largely as a result of their emissions from deforestation, despite relatively low totals from the use of fossil fuels.

Germany, in sixth place with 3.5% of cumulative emissions thanks to its coal-reliant energy industry, illustrates how some countries’ land sectors have become cumulative CO2 sinks rather than sources, as trees have returned to previously deforested areas.

(Note that the data used for this article is based on the scientific approach to accounting for land-use emissions, which differs from that used in the official inventories submitted to the UN. The difference, which relates to what is counted as a “human” versus a “natural” source or sink of CO2, was explored in a Carbon Brief guest post published earlier this year.)

India is in seventh place in the rankings, with 3.4% of the cumulative total_just above the UK, on 3.0%_ as a result of a higher contribution from land-use change and forestry. Japan on 2.7% and Canada, with 2.6%, close out the top 10 largest contributors to historical emissions. International transport emissions from aviation and shipping, which are almost always excluded from national inventories and targets, would rank 11th in the list if viewed as a “nation”.

Cumulative consumption emissions

One common argument in climate-justice conversations is that certain countries have reduced their territorial emissions at home, but continue to rely on high-carbon goods imported from overseas. Consumption-based emissions accounts give full responsibility to those that use the products and services rendered with fossil energy, tending to reduce the total for major exporters, such as China.

There are practical challenges to gathering such accounts, which rely on detailed trade tables. As such, they are only available for the years since 1990, even though international trade in carbon-intensive products has been going on throughout modern history.

Despite these limitations, it is possible to examine the impact of traded CO2 on countries’ cumulative emissions, as shown in the chart below. The grey bars show cumulative national emissions on a territorial basis, with the light grey chunks indicating CO2 associated with exports and the red chunks representing emissions embedded in imported goods and services.

Notably, the top 19 countries according to their cumulative consumption emissions are the same as the top 19 on a territorial basis_and none of the top 10 shift position in the rankings. This is despite some countries now having a much larger CO2 footprint than their territorial total.

(Chart: The 20 largest contributors to cumulative consumption-based CO2 emissions 1850-2021 Credit: Carbon Brief)

While the main rankings do not change as a result of using consumption-based emissions accounts, the shift does add to the share of responsibility accorded to wealthy nations. The US and Japan each gain 0.3 percentage points of the global cumulative total, while Germany and the UK add 0.2 points each, whereas China’s share drops by 1.1 points and Russia’s by 0.5.

Note that the consumption accounting used here only includes CO2 from fossil fuels and cement, hence Brazil and Indonesia’s cumulative totals barely change. Note also that the unavailability of consumption-based accounts before 1990 means that earlier carbon-intensive trade is excluded from the analysis. The UK, as the original “workshop of the world” in the 19th century, exported large volumes of energy and carbon-intensive goods.

Other industrialising nations, such as the US and Germany, did the same, playing, as one 2017 paper puts it, a similar role to the China’s today: “Today, China is often perceived as the workshop of the world, producing large amounts of cheap consumer goods for others. A century ago Britain and Germany (along with the United States) played a similar role both for Europe and globally.”

In 1890, nearly 20% of UK energy use related to exported goods, meaning a similar proportion of its CO2 emissions would have been allocated overseas on a consumption accounting basis. Consumption-based accounting still does not fully resolve the question of responsibility for emissions, however, given that both sides of a trade relationship are likely to gain financially.

In the modern context, only one side of that relationship has full sovereignty over the CO2-emitting activities involved_though it would have been a different story under historical colonial rule.

A third approach is to make fossil-fuel producers responsible for the CO2 released when their coal, oil or gas is burned. This idea is often mentioned in relation to the “scope 3 emissions” of oil companies, or when discussing major fossil-fuel exporters, such as Australia. However, national emissions on a production basis are not currently available and, without careful accounting, this could risk the double-counting of CO2 produced in one place and used elsewhere.

Cumulative per-capita emissions

The idea of national responsibility has other issues, including the unequal size, wealth and carbon intensity of present-day populations, as well as those of previous generations.

These issues apply both within and between countries. Moreover, countries themselves are somewhat arbitrary human constructs, resulting from accidents of history, geography and politics. With alternative borders, the ranking of historical responsibilities might look very different.

One way to attempt to untangle this is to normalise countries’ contributions to cumulative CO2 emissions according to their relative populations. Unlike cumulative historical emissions, which relate directly to current warming, these per-capita figures are not immediately relevant to the climate, explains Prof Pierre Friedlingstein, chair in mathematical modelling of climate systems at the University of Exeter. He tells Carbon Brief:

“What matters for the atmosphere and the climate is cumulative CO2 emissions. While cumulative per-capita emissions are interesting, they shouldn’t be interpreted as country shares of responsibility because they’re not directly relevant to the climate. You would have to multiply it by the country’s population to make that link to warming.”

Another way to think about this is to note that small countries with high per-capita emissions are still relatively unimportant for warming overall. For this reason, the table below excludes countries with present-day populations lower than 1 million people. (This removes the likes of Luxembourg, Guyana, Belize and Brunei.)

Carbon Brief’s analysis approaches the question of accounting for relative population sizes in two different ways. These approaches give markedly different results, highlighting the challenge of interpreting cumulative per-capita emissions.

The first approach takes a country’s cumulative emissions in each year and divides it by the number of people living in the country at the time, implicitly assigning responsibility for the past to those alive today. The table, below left, shows the top 20 countries on this basis, as of 2021.

The second approach takes a country’s per-capita emissions in each year and adds them up over time, with the result, as of 2021, shown in the table, below right. This gives equal weight to the per-capita emissions of the populations of the past and the present day.

Rank Country Cumulative emissions per population in 2021, tCO2 Rank Country Cumulative per capita emissions, tCO2 
1Canada1,7511New Zealand5,764
2United States1,5472Canada4,772
4Australia1,3884United States3,820
5Trinidad and Tobago1,1875Argentina3,382
8United Kingdom1,1008Malaysia2,342
9Germany1,0599Republic of Congo2,276
13New Zealand96213Zambia1,966
15Ukraine92215Cote d’Ivoire1,943
16Lithuania89916Costa Rica1,932
19Sweden77619Trinidad and Tobago1,842
20Paraguay73220United Arab Emirates1,834

I The top 20 countries for cumulative emissions 1850-2021 weighted by population in 2021 (left), versus the top 20 countries for cumulative per-capita emissions 1850-2021 (right). The ranking excludes countries with a population in 2021 of less than 1 million people.

Perhaps the most notable impact of accounting for the population is the absence, in the table above, of several of the top 10 for cumulative emissions overall, namely China, India, Brazil and Indonesia.

While these countries have made large contributions to global cumulative emissions, they also have big populations, making their impact per person much smaller. Indeed, those four countries account for 42% of the world’s population, but just 23% of cumulative emissions 1850-2021. In contrast, the remainder of the top 10, namely US, Russia, Germany, the UK, Japan and Canada, account for 10% of the world’s population, but 39% of cumulative emissions.

This is reflected in the weighting by current populations, in the table above left, where Canada ranks in the first place, followed by the US, Estonia, Australia, Trinidad and Tobago, and Russia.

For the larger countries on this list, their rankings reflect combinations of high deforestation rates during the 19th and mid-20th centuries_often when populations were much lower_along with high per-capita fossil fuel use in more recent decades. For others, the reasons are less obvious. Estonia, for example, has long relied on oil sands for most of its energy needs, meaning it has had high annual per-capita emissions. The Estonian government has pledged to phase out oil sands production by 2040.

(Note that as a former Soviet state, Estonia’s emissions before 1991 are estimated according to its share of the USSR’s total at that time, meaning there is more uncertainty than for most other countries.)

Trinidad and Tobago, a Caribbean island nation of just 1.4 million people, ranks highly thanks to its large oil and gas industry, which also feeds a sizeable chemicals sector. Turning to the cumulative per-capita ranking in the table, above right, the list is quite different, although it once again features Canada, Australia and the US in prominent positions.

New Zealand ranks at the top of this list because of extensive deforestation during the 19th century, when much of its native Kauri forest was cleared for its valuable timber. The country’s tiny population at the time consequently had very high annual per-capita emissions, with the cumulative total by 1900 making up around two-thirds of the total amassed by the present day.

Other countries on this list as a result of emissions from deforestation include Gabon, Malaysia and the Republic of Congo, as well as several South American nations. In terms of assigning “responsibility” for these emissions, this again raises difficult questions relating to colonisation and the extraction of natural resources by foreign settlers.

Read the full and original article at Carbon Brief I Analysis: Which countries are historically responsible for climate change?