The primary impact of volcanic eruptions on our climate is the cooling effect caused by sulphate aerosols. This is significant but is temporary, lasting only a few years post-eruption.

Volcanic eruptions release sulphur gases which, during significant explosive events, react with water to form stratospheric aerosols. These sulphate aerosols have a dual effect: they reflect solar radiation back into space and absorb it, causing heating in the stratosphere but cooling in the troposphere. For instance, the Earth’s surface cooled by approximately 0.5 degrees Celsius globally following the 1991 eruption of Mount Pinatubo in the Philippines, which expelled 20 million tons of sulphur dioxide gas. Due to their relatively short atmospheric lifespan—since they sediment out— even the most substantial eruptions lead to a cooling effect that persists for just a few years.

While volcanoes do emit carbon dioxide, the scale is significantly smaller compared to human-induced emissions. Research indicates that volcanic CO2 emissions to the atmosphere range between 150 to 270 million metric tons annually. In contrast, anthropogenic CO2 emissions—stemming from the combustion of fossil fuels and changes in land use—surpassed 36,000 million metric tons in 2008, as reported by a 2009 study in a peer-reviewed journal. This figure is more than 130 times greater than the volcanic CO2 output, making it clear that volcanic contributions to current greenhouse warming are minimal.

Alejandra Guerrero (PhD Candidate)