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Global carbon dioxide emissions

This chart shows how global fossil carbon dioxide emissions have increased since the 1990s. Note the drops in the early 1990s, in 2008, and the huge drop in 2020. ©  Global Carbon Project

According to the latest global carbon budget, the total global fossil carbon dioxide (CO2) emissions for 2020 were estimated to be 34 billion tonnes of carbon dioxide. This equates to 2.4 billion tonnes less carbon dioxide than was emitted in 2019. This represents a never-before-seen 6.7 per cent drop in emissions due to the slowdown in economic activity associated with the COVID-19 pandemic.

However, 2020 was an anomaly. Overall, global carbon dioxide emissions have increased by 61 per cent since 1990, though the rate of increase has varied. The primary driver of this increase has been the continued growth in the use of fossil fuel energies such as coal, oil and natural gas. Changes in the pace of that growths have often been associated with the rise or fall of major economies, such as China and the Soviet Union.

Encouragingly, the last decade has seen a slowdown in the rate of increase in emissions. Between 2010 and 2019 the rate of increase was just below 1 per cent per year, compared to an average increase of 3 per cent per year during the early 2000s. Emissions in 2019 didn’t grow much, if at all, when compared to 2018.

Main sources and sinks of carbon dioxide

This chart shows the sources and sinks of global carbon dioxide emissions since 1850. ©  Global Carbon Project

Burning fossil fuels (such as coal, oil and gas) is by far the major source of human-derived carbon dioxide emissions. This source alone, with small contributions from cement manufacturing, accounts for around 85 per cent of total emissions. Land-use change (such as deforestation) is responsible for the remaining emissions.

Of the activities that rely on burning fossil fuels, power production creates the most emissions (44 per cent of global emissions), followed by industry (22 per cent of global emissions) and surface transport (21 per cent of global emissions). Aviation accounts for a small 2.8 per cent of global emissions.

The extra carbon dioxide in our atmosphere has led to our oceans and land absorbing increasing amounts of carbon dioxide in response. In 2020, land and ocean sinks absorbed about 54 per cent of the total human-derived carbon dioxide emissions. This has the important benefit of slowing down climate change, but also has the serious impact of increased ocean acidification.

The remaining emissions stay in the atmosphere. This caused atmospheric carbon dioxide levels to increase by about 2.5 parts per million (ppm) in 2020. The extra carbon dioxide in the atmosphere is causing our climate to warm. The world’s climate will only stabilise when the level of atmospheric carbon dioxide does as well. In other words, global carbon dioxide emissions need to be net zero for our climate to stop warming. Net zero emissions means that the amount of emissions, if any still left, need to be equivalent to an amount of carbon dioxide being removed from the atmosphere (either by new vegetation or by the direct removal with machines yet to be fully proved).

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