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Do volcanoes produce more CO2 than humans?

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Volcanoes, those forces of nature feared and revered since time immemorial. Volcanoes are also the geological entities to which skeptics and even outright deniers of mankind’s role in current climate change tirelessly appeal.

Climate change deniers argue that the carbon dioxide (CO2) emissions from human activities are merely a faint glimpse compared to the CO2 injected into the atmosphere by volcanoes. Therefore, our influence on the climate would be negligible when compared to that of volcanoes. As a result, they see society’s efforts to mitigate a phenomenon that, according to them, is part of a natural cycle occurring over millions of years as a waste of time.

I must acknowledge that conspiracy theories, like the one I will address below, do have one redeeming quality: they provide an opportunity to learn science by investigating their degree of credibility. Science, after all, remains the best tool to challenge such claims.

Humans outpace volcanoes

Precisely because of their danger, volcanoes have been the subject of scrupulous study by the scientific community. Thanks to this research, we know quite precisely the amount of gases and other products emitted by volcanoes (both submarine and terrestrial) into the atmosphere and their effects on the climate.

To the dismay of those who deny human-induced global warming, scientific data unequivocally refutes their beliefs. It turns out that CO2 emissions from human activities surpass natural volcanic emissions by several orders of magnitude.

Vehicle congestion and pollution
Human activities, such as the burning of fossil fuels, changes in land use or deforestation, inject more CO2 into the atmosphere each year than all the active volcanoes in the world. Manish Swarup

Estimates from various sources (which can be consulted below) agree that annual volcanic CO2 emissions are equivalent to only a paltry 1% of human emissions, at most 2%. While volcanoes, considering together submarine and terrestrial volcanoes, emit between 150 – 450 million tons of CO2 per year, humans produced 59 billion tons in 2019 according to the sixth report of the Intergovernmental Panel on Climate Change (IPCC), i.e., more than 100 times that of volcanoes. In other words, it takes humans less than a week to generate the same CO2 as all the world’s volcanoes in a year.

To visualize the magnitude of this information better, pay attention to the following table:

CO2 emitting agent 

Million tons of CO2 per year

Human activities on a global scale (2019)

59 000

United States (2023)

5 900

Russia (2023)

2 670

Germany (2023)

682

Texas (USA) (2022)

663

Spain (2023)

285

Florida (USA) (2022)

231

Mount Pinatubo (eruption of June 15, 1991)

50 million tons in 9 hours

Cumbre Vieja (eruption of 2021)

14 – 42 million tons in 86 days

Mount St. Helen (eruption of May 18, 1980)

10 million tons in 9 hours

It can be seen how there are countries and even regions within those countries that inject significantly higher amounts of CO2 into the atmosphere than all the volcanoes in the world. It also highlights the low CO2 production of some of the most violent and famous eruptions of the last decades compared to anthropogenic emissions.

Volcanic eruptions and the cooling effect

There is another well-known fact that helps to disconnect volcanoes from the current global warming. Although it may seem counterintuitive, it is common for the climate to cool after a major eruption. This phenomenon becomes clearer when we understand the materials released by volcanoes during their eruptions.

In addition to greenhouse gases (CO2, methane, water vapor), volcanoes also eject ash and other gases such as sulfur dioxide (SO2). When SO2 reaches the stratosphere, it reacts with the surrounding water vapor, forming microscopic sulfate aerosol particles. These aerosols contribute to reflecting sunlight back into space, thereby reducing the amount of solar radiation reaching Earth’s surface and leading to cooling.

Mount Pinatubo eruptive column
Eruption of Mount Pinatubo in 1991. Richard P. Hoblitt

This phenomenon was observed after the eruption of Mount Pinatubo in 1991. The massive release of SO2 cooled the Earth’s surface by 0.5°C, an effect that persisted for two years following the eruption. Let us also recall the 1816 eruption of the Indonesian volcano Tambora, which robbed the Northern Hemisphere of its summer, precisely due to the massive ejection of ash and SO2 into the stratosphere.

It is clear, therefore, that the influence of volcanic activity on the climate warming of recent centuries is minimal compared to that of human activities. Major volcanic eruptions occur sporadically and have short-lived effects. In contrast, human activities take place every single day of the year, and their intensity shows little sign of decreasing. On the contrary, they tend to grow over time to support an ever-increasing population.

We can assert unequivocally that humans have become the primary driver of climate change, surpassing even the untamed forces of nature that are volcanoes.

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