Carbon dioxide (CO2) is a gas essential for life—animals exhale it, plants sequester it. It exists in Earth’s atmosphere in comparably small concentrations, but is vital for sustaining life. CO2 is also known as a greenhouse gas (GHG)—a gas that absorbs and emits thermal radiation, creating the ‘greenhouse effect’. Along with other greenhouse gases, such as nitrous oxide and methane, CO2 is important in sustaining a habitable temperature for the planet: if there were absolutely no GHGs, our planet would simply be too cold.

Since the Industrial Revolution, however, energy-driven consumption of fossil fuels has led to a rapid increase in CO2 emissions, disrupting the global carbon cycle and leading to a planetary warming impact. Global warming and a changing climate have a range of potential ecological, physical and health impacts, including extreme weather events (such as floods, droughts, storms, and heatwaves); sea-level rise; altered crop growth; and disrupted water systems.

If we extend our timeline back to 1750 and total up how much CO2 each country has emitted to date, we can calculate each nation’s ‘cumulative emissions’. The following visualization shows cumulative CO2 emissions representing the total sum of CO2 emissions since 1751, measured in milliontonnes.

The key drawback of measuring the total national emissions is that it takes no account of the nation’s population size. China is currently the world’s largest emitter, but since it also has the largest population, all being equal we would expect this to be the case. To make a fair comparison of contributions, we have to therefore compare emissions in terms of CO2 emitted per person.

In the map below CO2 emissions per capita through time are compared. Again, if we cycle through time by moving the slider below the map, we see that per capita emissions in most countries have continued to increase in line with development. However, if we look at the distribution of per capita emissions, large global inequalities remain.

With a few exceptions, there is an important north-south divide in terms of per capita emissions. Most nations across sub-Saharan Africa, South America and South Asia have per capita emissions below five tonnes per year (many have less than 1-2 tonnes). This contrasts with the global north where emissions are typically above five tonnes per person (with North America above 15 tonnes). The monthly emissions per capita in rich countries are mostly higher than the yearly emissions per capita in poorer countries. The largest emitter, Qatar, has per capita emissions of 50 tonnes per year (1243 times that of Chad, the lowest emitter).

Historically, CO2 emissions have been primarily driven by increasing fuel consumption. This energy driver has been, and continues to be, a fundamental pillar of economic growth and poverty alleviation. As a result, we can see that there is a strong correlation between per capita CO2 emissions and GDP per capita. Historically, where fossil fuels are the dominant form of energy, we therefore see increased CO2 emissions as an unintended consequence of development and economic prosperity.

While we see this general relationship between CO2 and GDP, there are outliers in this correlation, and important differences exist in the rate with which per capita emissions have been growing. These differences are exemplified in global inequalities in energy provision, CO2 emissions, and economic disparities.

The link between economic growth and CO2 described above raises an important question: do we actually want the emissions of low-income countries to grow despite trying to reduce global emissions? In our historical and current energy system (which has been primarily built on fossil fuels), CO2 emissions have been an almost unavoidable consequence of the energy access necessary for development and poverty alleviation.

In the charts below, we see energy use per capita on the y-axes, plotted against the share of the population living in extreme poverty (%) on the x-axis. In general, we see a very similar correlation in energy access (and also higher CO2 emissions) with lower levels of extreme poverty. Energy access is therefore an essential component in improved living standards and poverty alleviation

In an ideal world, this energy could be provided through 100% renewable energy: in such a world, CO2 emissions could be an avoidable consequence of development. However, currently we would expect that some of this energy access will have to come from fossil fuel consumption (although potentially with a higher mix of renewables than older industrial economies). Therefore, although the global challenge is to reduce emissions, some growth in per capita emissions from the world’s poorest countries remains a sign of progress in terms of changing living conditions and poverty alleviation.

With an understanding of the link between CO2 and global temperatures, as well as knowledge of the sources of emissions, an obvious question arises: How much could we reduce our emissions by, and how much would it cost? The possible cost-benefit of taking global and regional action on climate change is often a major influencing factor on the effectiveness of mitigation agreements and measures.

Credit and full story: Our World in Data – CO₂ and other Greenhouse Gas Emissions by Hannah Ritchie and Max Roser


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